In the first part of this work, I have explained the
two great divisions of life, together with the remarkable
differences, which distinguish the animal existing without,
from the animal existing within. I have discussed the
characters which are exclusively proper to the two lives,
and the particular laws, according to which they both of
them commence, are developed and end in the natural
order.
In this second part I shall inquire in what way they
accidentally finish, in what way their course is prematurely
arrested.
The influence of society suffers us but rarely to live
out the period which was intended us by nature; while
almost every other animal attains his natural end, such
end in the human species is become a sort of phenomenon.
The different kinds then of accidental death, should engage
the particular attention of the physician and physiologist.
Now this sort of death may happen in two ways: sometimes
it is the result of great disturbance excited in the
economy; and sometimes it is the effect of disease.
In general it is easy enough to discover, according to
what laws the functions are terminated in consequence of
any violent or sudden attack; of apoplexy, for instance,
great hemorrhagy, concussion of the brain, or asphyxia;
because in such cases the organs of the body, excepting
that which is immediately affected, are not the seat of
any peculiar lesion, and cease to act from causes diametrically
the contrary of those, which according to the common
course of things maintain them in action. Now as
these causes are partly known, their contraries may be
inferred; besides, we are capable of imitating these sorts
of death upon animals, and consequently of analyzing,
experimentally, their different phenomena.
On the other hand it is seldom in our power to produce
artificially in the bodies of animals the diseases of the
human species. Were we even possessed of such power,
we should gain but little knowledge from it: the laws of
life in fact are so changed, so modified, so altered in their
very nature, by the various morbid affections to which
the parts are subject, that but very seldom can we depart
from the known phenomena of the living animal, when
we undertake to inquire into those which it exhibits
in its dying moments. For such inquiries it would be
necessary to know what is that intermediate state between
health and death, in which the functions experience so
remarkable a change; a change, which has such infinite
varieties, and produces such innumerable sorts of disease.
But, where shall we find the physician, who will assert
that from the actual data of his art, he understands in
such intermediate state, the profoundly hidden operations
of nature?
In these researches then, we shall occupy ourselves
more especially on those sorts of death which I first
enumerated. Those, which have been mentioned in the
preceding paragraph will engage us only now and then:
besides, at my age I cannot be supposed to have acquired
a sufficient degree of medical knowledge to treat of them
with advantage.
The first remark, which the observation of the different
kinds of sudden death suggests, is, that in all of them the
organic life to a certain point may subsist, the animal life
being extinct; but that the latter is entirely dependent,
and lasts not for a moment after the interruption of the
former. The individual, who is struck with apoplexy
may live internally for many days after the stroke, externally
he is dead. In this case death commences with the
animal life: if on the contrary it exerts its influence in
the first place upon any of the essential organic functions—as
on the circulation in wounds or on respiration
in the asphyxiæ—the animal life is gone at once, together
with the sensible actions of the organic life.
The red and warm-blooded animal, loses his external
life at the moment when he ceases to exist internally,
the cessation of the phenomena of his organic life is a
sure index of his general death; indeed the reality of
death can be pronounced only from such datum; the
interruption of the external phenomena of life is in almost
every instance fallacious.
On what depends this difference of the manner in
which the two lives accidentally end? It is owing to the
mode of that influence, which they exercise the one over
the other, to the kind of bond, by which they are connected.
This mode of influence, this bond, appears to exist
between the brain on the part of the animal life and the
lungs, or heart on the part of the organic life. The action
of one of these three organs is essentially necessary to
that of the two others; and as they constitute the three
centres, in which are terminated all the secondary phenomena
of the two lives, whenever they cease to act, the
phenomena which depend upon them must cease also, and
general death ensue.
Physiologists have been at all times acquainted with the
importance of this triple focus; and have given the name
of vital to all those functions, which have their seat in it.
Under the point of view which at present engages our
attention their ideas on this head are well worthy of
notice, for every species of sudden death begins by the
interruption of the circulation, the respiration, or action
of the brain. In the first place, one of the three functions
ceases, then the others successively; so that to expose
with precision the phenomena of sudden death, we must
consider them as they take place in the three principal
organs, which we have mentioned.
We shall first inquire into those deaths, which begin
at the heart, and afterwards into those, which begin in
the lungs and in the brain. I shall explain in what way,
when one of these organs is affected, the others die; and
then demonstrate by what sort of mechanism the death
of the various other parts of the body ensues. Lastly I
shall determine from the principles, which I shall then
have laid down, the nature of the different species of
disease, which are peculiar to the heart, the lungs, and
the brain.
I shall evidently have determined what is the mode of
this influence, should I be enabled to establish in what
way the action of the heart is necessary to that of the
brain; for in this instance the cause of death will be no
other than the privation of the cause of life. Now the
heart can only act upon the brain in two ways; by the
nerves, or the vessels which serve as their connecting
medium. In fact these two organs have no other means
of communication.
It is evident that the nerves cannot be the agents of
such actions; it is the province of the brain to act by
means of the nerves. The different parts of the body
never influence the brain by such means, excepting in
the sympathies. If a bundle of nerves belonging to the
voluntary muscles be tied, the muscles indeed will cease
to act, but nothing will be changed in the cerebral
mass.[56]
I have ascertained by many experiments that the phenomena
of galvanism, which are propagated so energetically
from the brain towards the organs, which descend,
if I may so express myself, along the nerve, will hardly
ascend in a contrary direction. Apply the apparatus to
a nerve of the loins and the muscles of the upper limbs,
and when the communication is made, there will be
scarcely any contraction; but on the establishment of a
communication between the same nerve and the lower
limbs, a violent convulsive motion will instantly be occasioned.
I have even observed, on placing two metallic
plates, the one under the lumbar nerves, and the other
under the upper limbs, that the communication of the
two plates by means of a third metal, will cause a contraction
of the lower limbs, while the upper limbs remain
inactive, or move but feeble.[57]
These experiments are particularly applicable to the
relation of the heart with the brain; for not only is it true
that the section, ligature or compression of the cardiac
nerves are of little effect with regard to the functions of
the latter, but it is true also, as we shall presently see,
that they do not directly modify the movements of the
former. We may conclude that the vessels are the exclusive
agents of the influence of the heart upon the brain.
The vessels, as every one knows, are of two sorts—venous
or arterial—they carry black or red blood, the
latter answer to the left side, the former to the right side
of the heart. Now their functions being very different,
the action of one of the portions of this organ on the
brain, can never be the same as that of the other portion.
We shall inquire in what way they both of them act
upon it.
In naming these two portions, I shall not make use of
the expressions of right and left to distinguish them, but
of those of the red-blooded and the black-blooded heart,
for each of these portions of itself is an isolated organ,
distinct from that to which it is applied, and in the adult
especially so. In fact there are two hearts, the one arterial,
the other venous, notwithstanding which, we can
hardly employ these adjectives for the purpose of designating
them, since they both alike possess their arterial and
venous appendages. On the other hand, they are neither
of them situated exactly to the right or to the left, are
neither of them exactly forwards or backwards. Besides
which these latter denominations would not apply to
animals.
The red-blooded ventricle and auricle, exert their influence
upon the brain by means of the fluid which they
send thither through the carotid and vertebral arteries.
This fluid may excite the cerebral organ in two ways.
1st. By the movement, with which it is directed. 2nd.
By the nature of its colouring principle.
It is easy to prove that the movement of the blood is
necessary to the life of the brain. Expose the brain of
an animal in part, and tie the carotids. In such case the
cerebral movement will be sometimes weakened, and then
the animal will be stupified, at other times the vertebral
arteries will exactly supply the place of the carotids, and
then there will be nothing deranged in the principal
functions of the brain; for there is always a relation
existing between the alternate rise and fall of the cerebral
mass, and the energy of life which it displays.[58]
In general, the obliteration of the carotids is never
suddenly mortal. Animals will live without them, at
least for a certain time. I have kept dogs in this state
for several days and have afterwards made use of them
for other experiments: two however died in the course
of six hours, after the application of the ligatures.
After having made the above experiments which go
very far to the establishment of the principle which I am
labouring to prove, let a piece of the cranium be taken
from another animal and tie the vertebral and carotid arteries.
The movement of the brain will then be entirely
interrupted and the animal immediately die.
The impulse, which proceeds then from the influx of
the blood into the brain, is a condition essential to the
functions of this organ, but other proofs may be adduced,
for the establishment of the truth of this assertion.
1st. There are a number of compressions, which can
only act by preventing the brain from being duly affected
by such impulse. A collection of pus, or blood, will
often put a stop to all the functions, which relate to the
perception, memory, and voluntary motions of the individual.
Let such compression be removed and his sensibility
will immediately re-appear. In such case, it is
manifest that the brain was not disorganized, but only
compressed, and in a state incapable of being excited by
the heart.[59]
I do not think it necessary on this subject to cite cases.
All authors, who have treated of wounds of the head, are
full of them. I shall content myself with remarking,
that the same effect may be artificially produced in our
experiments upon animals, and that accordingly as the
brain is compressed or free, the creature will be insensible,
or the contrary. According to the degree of the
compression, will be the degree of the stupor.
2dly. There are reptiles, in the brain of which no
motion whatever is occasioned by the heart. The frog
is of this species. On raising the upper portion of the
cranium, and exposing the brain, there cannot be perceived
the slightest motion. Now in this species, and
that of the salamander, the influx of blood may be cut off
from the cerebral organ without occasioning the immediate
death of the animal. The voluntary muscles for
instance continue to act; the eyes to exhibit a lively appearance,
the tact also of the creature is manifest for some
time after the heart has been taken away, or the double
branch which proceeds from the single ventricle of these
animals has been tied.[60] I have frequently repeated these
experiments, and have constantly found the effect the
same.
3rd. It is a general observation, that those animals
which have a long neck, and in which the heart for that
very reason is not so capable of exerting a lively influence
over the brain, have a more limited intellect, and
the cerebral functions less marked. On the contrary a
very short neck, and the approximation of the heart to
the brain very generally are found to coincide with the
latter. Similar phenomena are sometimes observed in
men. They who have the neck particularly long are
dull, they who have it short, for the most part intelligent
and lively.
From these many facts we may confidently assert, that
one of the means, by which the heart maintains the brain
in action, consists in the habitual movement, which it
impresses on it.
But this movement is essentially different from that
which in the other viscera, such as the liver, or spleen,
is derived from the same cause. In these it is little
manifest, in the brain it is very apparent; the reason is
evident; the large arterial trunks of the brain, are situated
at its base, between the brain and its bony parietes;
in consequence of which, at each diastole, the vessels
experience a resistance from the bone, which is communicated
immediately to the cerebral mass. At such time
the brain is really lifted, just in the same way as we see a
tumour lifted by the arteries which creep along the bones
beneath it; and instances of this are frequent. So apparent
indeed is the motion of tumours when they are
situated over the carotid, as it lies upon the vertebral
column, or over the femoral artery, immediately after its
passage under the crural arch, as often to occasion doubts
with respect to their nature.
But no other organ is enclosed within a bony cavity;
the motion of the arteries every where else, is lost in
the surrounding cellular substance, or soft parts. Such
motion, then, is unessential to the functions of the liver,
the kidney, and other analogous viscera.
The integrity of the functions of the brain, is not only
dependent on the mere motion, but on the sum also of
the motion communicated. It is equally impaired by too
much, or by too little motion. Of this assertion the
following experiments are proofs.
1st. Inject water by the carotid of a dog; the presence
of this fluid in the brain is not pernicious, and the animal
will live very well, when the injection has been skilfully
made. But if it be pushed with violence, the cerebral
action will immediately be troubled, and often cannot be
restored.[61] In every experiment, there will be found to
exist a relation between the force of the impulse and the
state of the brain; if the pressure be but a little augmented,
its effects will be instantly seen in the agitation of the
countenance of the creature; if relaxed, a corresponding
calm will succeed; if increased to the highest pitch, it
will immediately occasion death.
2dly. If the brain be exposed, and an artery afterwards
opened, so as to produce a considerable hemorrhage, the
motion of the brain will be diminished in proportion as
the afflux of the blood to it is diminished, and finally
will cease entirely. Now, according to all these various
degrees of diminution, which may be observed in the
movements of the brain, will be the corresponding weakness
of the cerebral influence as it is discoverable in the
state of the eyes, the touch, and the voluntary motion of
the animal.[62]
Hence it is easy to see, why a state of prostration and
languor is always the consequence of great hemorrhage—and
from what has been said above we may conceive the
reason, why the arterial system of the brain has been at
first concentrated at its base, while the larger venous
trunks are almost all of them situated on the convexity
of its surface. The base of the brain is small and easily
moved, the convexity large and little capable of transmitting
motion, such as could be made upon it by vessels.
Besides, it is at the lower part of the brain that exist its
particular and essential forms. The lesions of these are
mortal, and consequently their functions must be important.
On the contrary, experiment and observation alike
have proved, that very little derangement follows, from
cutting or rending the substance of the upper part of this
organ. Hence also we may see the reason, why its
natural defences towards its base, are constituted in such
way as to be almost impenetrable, and why at its upper
surface, it is less protected. Now, where its life is indispensable,
and its action absolutely necessary, it should
naturally receive the first and undiminished impulse of
its excitant. We may conclude, that the interruption
of the action of the red-blooded heart is the occasion of
interruption in the action of the brain by annihilating its
movement.
But this movement is not the only means by which
the influence of the heart is exerted on the brain; for if
it were so, we might easily reanimate the enfeebled functions
of the latter, by injecting it with water at the same
time through both the carotids. If pushed with an equal
force, the black blood and the red blood alike would be
capable of keeping up its action; but this, as we shall
presently see, is not the fact.
The heart, then, acts upon the brain by the nature of
the fluid which it sends thither; but as the lungs are the
focus, where the blood undergoes an alteration, we shall
refer the examination of its influence upon the cephalic
system, to the chapter in which we shall treat of the
relation of this system, with that of the lungs.
It very rarely happens that general death commences
by that of the venous auricle and ventricle. On the
contrary, they are almost always the last in action, and
when they cease to act, the brain, the lungs, and the red-blooded
heart have already ceased to exhibit their respective
phenomena. Nevertheless the contraction of these
cavities may be annihilated, or rendered at least inefficacious
with regard to the circulation, from the rupture of
an aneurism or similar causes; in which case the brain
becomes inactive and dies, as we have shewn it to do in
the preceding section, from want of movement.
There is another kind of death of the brain depending
on the interruption of the transmission of blood from the
head to the heart, as when the jugulars are tied. The
venous system, in consequence, is glutted and the brain
compressed, from the continued afflux of the red blood
into its arteries; but the phenomena of this sort of death
are already sufficiently known.
In the present chapter it is my intention to examine a
species of death, the principle of which by many physiologists
has been placed in the heart, but which appears
to me to affect the head only; I mean that death which
may be occasioned by the injection of air into the
veins.
It is generally known, that as soon as any quantity of
this fluid is introduced into the vascular system, the movements
of the heart are accelerated, that the creature is
much agitated, cries with pain, is convulsed, and soon
after deprived of its animal life, but lives organically for
a certain time, and then invariably dies.[63] Now, what
is the organ so readily affected by the contact of air? I
affirm it to be the brain, and not the heart; and maintain
that the circulation is annihilated, only because the
cerebral actions have previously been so.
For, in the first place, in this kind of death, the heart
continues to beat for some time after the cessation of the
animal life, and consequently for some time after that of
the action of the brain.[64]
Secondly, By injecting air into the brain through one
of the carotids, I have caused the death of the creature
just in the same way as when air is introduced into the
veins; excepting only with a previous palpitation of the
heart.[65]
Thirdly, Morgagni has cited a number of cases of sudden
death, the cause of which should appear, from his
remarks, to be the repletion of the blood vessels of the
brain by air, which had been developed there spontaneously,
and which he says, by its rarefaction, compressed
the origin of the nerves. I cannot suppose that such
compression can be effected by the very small quantity
of air, which, when injected into the carotid, is sufficient
to occasion death; accordingly, I should doubt whether
this compression were real in the cases adduced, but for
this, they are not the less important. Whatever be the
manner in which it kills, air is fatal whenever introduced
into the brain, and this is the essential point. It
is with the fact that we have to do and not the manner.[66]
Fourthly, As often as an animal is killed by the insufflation
of air into one of its veins, I have ascertained that
the whole of the red-blooded, as well as the black-blooded
heart, is full of a frothy blood, mixed with air bubbles;
and that the carotids, and vessels of the head, contain a
similar blood; such blood must act upon the brain, in the
same manner as it does in the two sorts of apoplexy, of
which we have just been making mention.
Fifthly, If air be pushed into one of the divisions of
the vena portæ from the side of the liver, it oscillates in
the greater trunks of that organ for a considerable length
of time, and arrives but slowly at the heart.—In this
instance I have observed, that the animal experiences,
only after a certain interval, those affections which are
sudden when the fluid is injected into the veins of the
principal system.[67]
Sixthly, The rapidity with which, in certain experiments,
the annihilation of the cerebral action succeeds to
the insufflation of air into the veins, might almost persuade
us that such phenomenon is occasioned, as it is in
wounds of the heart and syncope;—but 1st. The most
simple inspection is sufficient to shew us that the heart
continues to act after the apparent death of the animal.—2dly.
As the motions of the heart are prodigiously accelerated
by the contact of the foreign fluid, they push on
the frothy blood with an extreme velocity, and hence we
have the reason, why the brain in such case is so rapidly
affected.
Seventhly, Were the cerebral action in this sort of
death interrupted for want of movement from the heart,
it would happen as it does in great hemorrhages of the
aorta; that is to say, without violent convulsion. But
here, on the contrary, the convulsion is extremely violent,
immediately after the injection, and consequently,
announces the presence of an irritating substance on the
brain.
We shall conclude, that in the accidental mixture of
air with the blood of the venous system, it is the brain
which dies the first, and that the death of the heart is the
consequence of the death of the brain. I shall explain
in another place, in what way this phenomenon is occasioned.
The lungs are the seat of two very different sorts of
phenomena. The first, which are entirely mechanical,
are relative to the rise and fall of the ribs and diaphragm,
to the dilatation and contraction of the air vessels, and to
the entry and exit of the air, which is the effect of these
movements. The second, which are purely chemical,
may be referred to the different alterations, which the
air and blood experience.
These two sorts of phenomena have a mutual dependence
on each other. Without the mechanical, the chemical
changes could not be made; without the chemical
changes, the blood would cease to become an excitant to
the brain, in consequence of which that organ would no
longer operate upon the diaphragm or intercostal muscles;
the muscles themselves would then become inactive, and
the motions of the thorax be annihilated. These phenomena,
however, are put an end to in a different manner
by the death of the heart, accordingly as it happens on
one or the other side.
The heart has certainly no influence over the mechanical
functions of the lungs, but it contributes essentially
to produce the chemical changes which are made there,
by sending thither the fluid which is destined to undergo
a change. When its functions then are interrupted as
may happen from wounds or be occasioned by ligature,
the chemical changes which should be made in the blood,
are suddenly suppressed; though the air continue to
enter into the lungs, from the dilatation and contraction
of the chest.
Meanwhile there arrives nothing at the red-blooded
heart, or[68] so little as to be insufficient for the production
of the cerebral movements. The functions of the brain
are consequently suspended, and of course the movements
of the diaphragm and ribs.
Whenever from wound, ligature, or aneurism, the
functions of the red-blooded heart or aorta cease, the functions
of the lungs are terminated in the following order:
1st. There is no further impulse made upon the brain.
2dly, No further movement of that organ.[69] 3dly, No
further action exercised upon the muscles. 4thly, No further
contraction of the intercostals or diaphragm. 5thly,
The mechanical functions of the lungs cease. 6thly,
Their chemical functions cease.
In the former case, the chemical changes could not be
made for want of blood. Here they cannot be made for
want of air. Such is the difference in the death of the
lungs, in consequence of that of the heart, according
as the latter is affected. But as the circulation is very
rapid, there cannot be but a very short interval between
the interruption of the chemical and the mechanical functions
of the lungs.
I shall divide this chapter, as the preceding one, into
two sections. In the first I shall examine, how the death
of the red-blooded heart, in the second how the death of
the black-blooded heart, is the cause of the death of all
the parts of the body.
All the functions belong either to the animal, or to the
organic life. Hence the difference of their classes. Now
the death of those of the first class, in consequence of
lesions of the red-blooded auricle and ventricle, is caused
in two ways, and first, because the brain in such case is
rendered inert from want of impulse, and can neither
have sensations, nor exercise an influence over the locomotive
and vocal organs.
Accordingly, all this order of functions is stopped, as
when the encephalic mass has experienced a violent concussion.
It is in this way that a wound of the heart, or
the bursting of an aneurism, annihilate all our relations
with external objects.
So strict a connexion between the movement of the
heart, and the functions of the animal life, is not observable
in those animals in which the brain, in order to act,
does not require the habitual stroke of the blood. Tear
away the heart of a reptile, or tie its large vessels, and
it will continue for a long time to move and have sensations.
Besides, supposing even that the action of the brain
were not to be suspended from lesions of the red-blooded
heart, the animal life would not, on that account, be the
less put an end to; because to the exercise of the functions
of this life, is attached as a necessary cause, the
excitement of its organs by the afflux of blood into them:
now this excitement, both here and every where else,
depends upon two causes.—1st, On the movement impressed,
and 2dly, On the nature of the blood. At present
I shall only examine the first mode of influence; the
latter will come under our consideration, when we speak
of the lungs.
Habitual motion is necessary to all the parts of the
body alike, is a condition essential to the functions of the
muscles, the glands, the vessels, and the membranes, &c.
But this movement, which is partly derived from the
heart, is very different from that which is communicated
by the blood to the brain.
The latter organ receives an impulse by which the
whole of its mass is visibly raised, an impulse, in the
intermission of which the whole of its mass subsides.
On the contrary, the interior movement, by which its
particles are affected, is scarcely marked at all: and this
depends upon the smallness and the delicacy of the vessels
by which its substance is penetrated.
The contrary of this appearance is observed in the
movement occasioned in the other organs by the influx
of the blood into them: we see them neither rise nor
subside; there is nothing like a general impulse made
upon them, because, as I have said, such impulse is lost
from the little resistance of the surrounding parts. On
the contrary, they are penetrated by vessels of considerable
magnitude, which create an intestine motion, oscillations,
and impulses adapted to the actions of the tubes,
lamellæ, or fibres, of which they are composed. This
difference of movement may be easily conceived, by comparing
the manner in which the brain on the one hand,
and on the other the liver, the spleen, the muscles, or
the kidneys receive their blood; indeed it is requisite
that the brain should be distinguished from the other
organs, in the manner of receiving its impulses, because
it is enclosed in a case of bone, and consequently abstracted
from the thousand other causes of agitation, to which
the other parts of the body are exposed.
For we may remark, that all the other organs have
about them a number of agents, which are destined to
supply the place of that general impulse, which is wanting
to them on the part of the heart. In the breast, the
intercostals and diaphragm are continually rising and
falling; the lungs and the heart are successively the seat
of a dilatation and contraction. In the abdomen, there
is an uninterrupted agitation produced, by the influence
of respiration upon its muscular parietes; an incessantly
variable state of the stomach, intestines and bladder.
Lastly, from the various contractions of the muscles, the
limbs have a still more evident cause of movement.
Nevertheless, it is probable that every one of the
organs, as well as the brain, has a general though obscure
movement impressed upon it, from the pulsation of the
arteries; and hence, perhaps, we have the reason, why
the greater number of the viscera, receive the impulse
of the red blood upon their concave surfaces, as may be
seen in the kidneys, the liver, the spleen, and the intestines.
By such disposition, the impulse of the heart is
less divided.[70]
From what has now been said, we may add another
reason to that which we have before given, for establishing
in what way the functions of the animal life are
interrupted from cessation of action in the red-blooded
heart. We may now also begin to explain the same
phenomenon in the organic life. The reason of such
interruption in both the lives is the same. It is as follows:
1st. In the case of death affecting the red-blooded
heart; the intestine movement, which proceeds from the
manner in which the arteries are distributed within the
substance of all the organs, both of the one and the other
life, is suspended; hence there exists no farther cause of
excitement for the organs: they must consequently die.—2dly.
The causes of the more extensive and general
movements of the organs are abstracted; for almost all
these causes depend upon the brain. We respire and
move, only while the brain is alive: but as the brain
must be in a state of collapsus, as soon as it ceases to
receive the impulse of its blood, its influence must be
evidently annihilated.
Hence it follows, that the heart exercises over the
different organs two modes of influence; the one direct
and immediate, the other indirect, and made through the
medium of the brain, so that the death of the organs in
consequence of the death of the heart, is immediate or
mediate.
We have sometimes examples of partial death, analogous
to this sort of general death. Thus, when the
circulation is impeded in a limb, and the red blood no
longer distributed to its parts, such parts become at first
insensible and paralytic, then gangrenous. The operation
of aneurism furnishes us with too many instances of
this phenomenon, which by ligature, may be produced
also in the living animal. Undoubtedly the principal
cause of death in these cases, is the want of that stimulus
which it is the business of the particles of the red blood
to create, in contradistinction to those of the black blood,
but the absence of the intestine movement in question, is
by no means a less real cause of such death.
As for the interruption of the nutritive process, it
cannot be admitted as a cause of the symptoms which
succeed after the obliteration of a large artery. The
slow, the gradual, and insensible way, in which this
function is performed, does not accord with the sudden
and instantaneous production of those symptoms, especially
as they affect the animal life; for this is annihilated
in the limb at the very instant when the blood ceases to
flow into it, just in the same way as it is, when by the
section of its nerves, the influence of the brain is abstracted.[71]
Besides the preceding causes, which, when the heart
is dead, suspend in general the whole of the animal and
organic functions; there is another cause of death which
especially affects the greater number of the latter, such
as the processes of nutrition, exhalation, secretion, and
therefore digestion, which is only performed by means of
the secreted fluid. This cause of death to which I refer,
consists in the necessary stop which is put to these different
functions, in consequence of their no longer receiving
the materials upon which they are exercised. Nevertheless,
such term arrives by degrees only, because they
receive the materials on which they act, from the capillary,
and not from the general circulation. Now the
capillary circulation, is only subject to the influence of
the insensible contractile powers of the parts in which it
is performed; and is exercised independently of the heart,
as may be seen in the greater number of reptiles, where
the heart may be taken away, and the blood be notwithstanding
observed to oscillate for a long time afterwards
in the minuter vessels.[72] It is manifest, then, that whatever
quantity of blood is left in the capillary system at
the period of the death of the heart, will for some time
afterwards be sufficient to keep up the functions in question,
and that such functions in consequence will only
gradually cease.
The following is a general view of the manner in which
the annihilation of all the functions succeeds to the interruption
of those of the heart.
The animal life is terminated—1st, Because the organs
of which it is composed, are no longer excited without,
by the movement of the neighbouring parts, nor within,
by the blood.—2dly, Because the brain, from want of
excitement, can no longer be a cause of excitement.
The organic life is terminated—1st, Because, as in the
animal life, there is a want of external and internal excitement
for its different viscera.—2dly, Because there is a
want of the materials on which its functions are particularly
exercised.
There are a number of other considerations, however,
besides those which we have mentioned, which prove the
reality of the excitement of the organs, from the movement
communicated to them by the blood, as well as the
reality of the cause, which we have asserted to be that of
their death, when such excitement ceases.
For, 1st.—The organs which are penetrated only by
the serum of the blood, such as the hair, the nails, the
tendons, and cartilages, enjoy a less degree of vitality,
and a less energetic action, than those in which the blood
is made to circulate, either immediately by the heart, or
by the insensible contractile powers of the parts themselves.
2dly.—When the white organs are inflamed, they
receive an augmentation of life, a superabundance of sensibility,
which frequently put them on a level in many
respects with those organs, which in their natural state
are endowed with the highest degrees of life and sensibility.
3dly.—Those organs which habitually receive the influx
of the red blood, when inflamed, exhibit, in every instance,
a local exaltation of the phenomena of life. In the two
preceding instances, it is true, indeed, that the change of
vital powers, precedes in point of time, the change which
is made in the circulation; the organic sensibility of the
part, has been augmented before the blood is carried
thither in greater quantity; but afterwards it is the afflux
of such increased quantity of blood, which keeps up the
unnatural action which has been established. A determined
quantity of blood in the ordinary state of the part,
is necessary to the maintenance of that state; but when
the part receives a double or triple increase of energy,
its excitant also must be doubled or tripled; for in the
exercise of the vital powers, there are always three things
to be remarked; the power inherent in the organ; the
excitant which is foreign to it; and the excitement which
is the product of the two.
4thly.—It is doubtless, for this reason, that the organs
to which the blood is habitually carried by the arteries,
enjoy a degree of life, proportionate to the quantity of
fluid by which they are injected. Such phenomenon
may be observed in the glans penis, in the corpora cavernosa,
in the nipple, in the skin of the face, and the
actions of the brain, whenever the blood is directed with
impetuosity towards them.
5thly.—The whole of the circulatory system, is thrown
into greater action from the exaltation of the whole of the
vital phenomena, just in the same way as the particular
circulation of any part is augmented, when the particular
phenomena of the life of that part are increased. The
use of spirituous liquors, and spices to a certain quantity,
is followed for a time by a general increase of energy in
the powers of the system. The access of inflammatory
fever will double and triple the intensity of life.
In these considerations I have only regarded the movement
which is communicated to the organs by the blood.
In another place I shall call the attention of the reader
to that species of excitement, which is produced by the
nature of the blood, by the contact of its component
particles when in a state of oxydation or otherwise, with
the different parts of the body. The reflections which I
have offered, will be amply sufficient to convince us how
much the blood, independently of the materials which
it conveys with it, by its simple influx, is necessary to
the activity of the organs, and consequently how much the
cessation of the functions of the heart, must influence the
death of the organs.
Whenever the heart ceases to act, general death is
produced in the following manner:—1st. For want of
excitement the cerebral actions are annihilated, and consequently
an end is immediately put to all sensation,
locomotion, and utterance. Besides, for want of excitement
on the part of the blood, the organs of these functions
would cease to act, even supposing that the brain
were to remain unaffected, and exert upon them its accustomed
influence. Thus the whole of the animal life is
suddenly suspended, and at the instant of the death of the
heart, the individual is dead to what surrounds him.
The interruption of the organic life, which has commenced
by the death of the heart, is produced at the same
time by that of the lungs. The brain being dead, the
mechanical functions of the lungs must cease: the chemical
functions of the lungs must cease also, for want of
the materials on which they are exerted: the latter are
directly interrupted, the former through the medium of
the brain.
After this the progress of death is gradual. The secretions,
the exhalations, the nutritive actions are put an end
to. The latter are first arrested in those organs which
receive the more immediate impulse of the blood, because
in these, such impulse is necessary to the performance of
the functions. The paler organs are less dependent on
the influence of the heart, and consequently must be less
affected by the cessation of its action.[73]
In the successive termination of the latter phenomena
of the internal life, the vital powers continue to subsist
for some time after the loss of the functions: thus, the
organic sensibility, and the sensible and insensible contractilities
survive the phenomena of digestion, secretion,
and nutrition.[74]
The vital powers continue to subsist in the internal
life, even when the corresponding powers of the animal
life, have suddenly become extinct: the reason is plain:
the power of perceiving and moving organically does
not suppose the existence of a common centre; for the
animal perceptions and motions, the action of the brain
is requisite.
The phenomena of death are concatenated in the above
order in all aneurismal ruptures, in all wounds of the
heart or larger vessels, in all cases of polypi formed in
the cardiac cavities,[75] of ligature artificially applied, of
compression exercised on the parietes of the heart by
humours, abscesses, &c. &c.
It is in this manner also that we die from sudden affections
of the mind. The news of a very joyful, or a very
melancholy event, the sight of a fearful object, of a
detested enemy, of a successful rival, are all of them
causes capable of producing death. Now in all these
instances, it is the heart, which is the first to die, the
heart, whose death successively produces that of all the
other organs, the heart, on which the passion is exerted.
And hence we are led to some considerations on syncope,
an affection exemplifying in a less degree the same
phenomena, which in a greater one, is offered us in cases
of sudden death.
The causes of syncope are referred by Cullen to two
general heads: Of these there is one set which according
to him affect the brain, another set which affect the heart.
Among the first, he places the more violent impulses on
the mind, and various evacuations, but it is easy to prove,
that the brain is only secondarily affected in syncope produced
by passion, and that it is the heart, whose functions
in all these cases are the first to be interrupted. The
following considerations, if I am not mistaken, will leave
but little doubt on this head.
1st.—I have proved, in speaking of the passions, that
they never affect the brain in the first place; that the
action of this organ, in consequence of their development,
is only secondary, and that every thing relating to
our moral affections has its seat exclusively in the organic
life.
2dly.—The phenomena of syncope when produced by
lively emotion, are similar in every respect to those of
syncope, the effect of polypi or dropsy of the pericardium,
but in the latter, the affection of the heart is the primary
one, and should in consequence be the same in the former
sort of syncope.
3dly.—At the moment when syncope takes place, we
feel the attack at the heart, and not in the brain.
4thly.—In consequence of lively passions, which may
have occasioned syncope, we find that the heart and not
the brain becomes diseased, nothing is more common than
organic affections of the former from sorrow, &c. The
different sorts of madness, which are produced by the
same cause, for the most part have their principal seat in
some of the viscera of the epigastrium, and in such case,
the irregularity of the cerebral action is the sympathetic
effect of the profound affection of the internal organ.[76]
5thly.—I shall prove hereafter, that the cerebral system
does not exert any direct influence over that of the circulation;
that there is no reciprocity between the two, and
that the changes of the first are not followed by similar
changes in the second, however much the changes of the
second may modify the first. Destroy all nervous communication
between the brain and the heart, and the
circulation will go on as usual; but if the vascular communications
be intercepted, the cerebral action vanishes
at once.
6thly.—Palpitations and other irregular movements of
the heart are often the effect of the same causes, which
in some individuals are the occasion of syncope. In such
cases, it is easy to discover the seat of the affection, and
such smaller effects of the passions on the heart, are
very well calculated to throw light upon the nature of the
greater.[77]
From these many considerations, we may conclude that
the primitive seat of the attack in syncope, is the heart,
which does not cease to act, because the action of the
brain has been interrupted, but because it is the nature of
some of the passions in such way to affect it, the brain
at the same time, suffering a temporary death, because it
no longer receives the fluid, which is necessary to its
excitement. The nature of syncope is well enough illustrated,
by the vulgar expression of being sick at heart.
It is of no importance to our present purpose, whether
syncope depend on polypi, on aneurism, or be the result
of some violent emotion. The successive affection of the
organs is always the same. They die for the moment in
the same way, as they really perish when the heart is
wounded, or a ligature put upon the aorta. In the same
manner also are those sorts of syncope produced, which
succeed after any great evacuation of blood, pus or water.
The heart is affected from sympathy, the brain for want
of its excitant.[78]
Those cases of syncope which are occasioned by peculiar
odours, by antipathies, &c. appear also to be attended
with the same progression of symptoms, though their
character be much less easily understood. There is a great
difference between syncope, asphyxia, and apoplexy, in
the first it is by the heart, in the second by the lungs, in
the third by the brain that begins the general death of the
body.
Death, as it happens in consequence of disease, in general
exemplifies a concatenation of these different symptoms.
The circulation, respiration, or cerebral action
cease, the other functions are afterwards interrupted of
necessity, but in these sorts of death, it rarely happens
that the heart is the first to die. This however is sometimes
the case. After long continued suffering, great
suppuration, and sometimes, in dropsy, certain fevers,
and gangrenes, one fit of syncope comes on after another,
at last a longer one succeeds, and the patient dies, but
whatever be the part affected, whatever the diseased
viscus or organ, whenever the phenomena of death commence
by the heart, they succeed each other as we have
described them to do in sudden death, from lesion of that
organ. In other cases, the heart is the last to act, is the
ultimum moriens.
In general, in morbid affections, we much more commonly
observe the ingress of death to be made by the
lungs, than either by the heart, or the brain.
Whenever disease is terminated by syncope, the lungs
are found to be almost empty, and if not affected by any
organic disease, are collapsed, occupy a part only of the
cavity of the thorax, and are of their natural colour.
The reason of this anatomical fact is simple. The
circulation which has been suddenly interrupted, has not
had time to fill the vessels of the lungs, as happens when
death begins, by affecting the lungs or the brain. The
truth of this fact I can vouch for, having frequently
ascertained it by dissection, and in general, as often as
death commences by the heart, or the larger vessels, such
vacuity of the lungs may be considered as universal.
I have remarked it in the bodies of persons who have
died from great hemorrhage from wounds or aneurismal
rupture and violent passion, as well as in those who have
suffered by the guillotine. The same phenomenon may
be seen, by inspecting the lungs of any animal, which is
killed in our butcheries.
In killing the animal slowly by the lungs, that organ
might be filled with blood. Its taste would then be different
from that which it naturally possesses, and resemble
that of the spleen. Our cooks know well how to
take advantage of that state of infiltration in which the
latter viscus is generally found.
We have already said, that the functions of the lungs
are of two kinds, mechanical and chemical. Now the
activity of this organ ceases sometimes by the former,
and sometimes by the latter of these functions.
Any wound, which exposes the lungs on both sides,
for a considerable extent, occasions their sudden collapse;
any division of the spinal marrow, which suddenly paralyses
the intercostals, and the diaphragm; any very
strong compression exerted at the same time upon the
whole of the thorax, and the parietes of the abdomen,
any sudden injection of a large quantity of fluid into this
cavity, are all of them causes which begin the death of
the lungs, by putting an end to their mechanical functions.
Those which influence in the first place their chemical
functions, are the different sorts of asphyxia, strangulation,
submersion, and a vacuum, in whatever manner
produced.
The interruption of the functions of the heart, can
only succeed in two ways to that of the mechanical functions
of the lungs: 1st. Directly, because a mechanical
impediment is put to the circulation of the blood, by a
state of collapse in the lungs. 2dly. Indirectly, because
in such state the lungs no longer receive the materials,
upon which their chemical functions are exerted, and
therefore cannot transmit them to the heart.
Physiologists have all of them admitted the first mode
of interruption, in the Pulmonary circulation. Reflected
on themselves, the vessels of the lungs have not appeared
to them, to be capable of transmitting the blood, on
account of the numerous angles which they make. This
idea they have borrowed from the phenomena of hydraulics,
and it is their reason for the death which ensues, in
consequence of a too long continued expiration.
Notwithstanding all which, it has been proved by
Goodwyn, that in such case there remains a sufficient
quantity of air in the air vessels, for dilating them enough
to allow of the mechanical passage of the blood; he
proves in consequence, that an unnatural permanence of
the state, in which the lungs are placed from the act of
expiration, does not affect the blood in the way, which is
commonly believed. This is one step towards the truth,
but we shall approach it much more nearly, and even
attain it, should we be able to prove, not only that there
remains a sufficiency of air in the lungs to permit the
transmission of the blood, but that the very folds produced
in the vessels by a state of collapse in the organ
are not a real impediment to its course. The following
observations and experiments will assuredly determine
this fact.
1st.—I have already proved, that a state of fulness or
emptiness in the stomach, and in all the hollow organs in
general, produces no apparent change in the state of their
circulation; and that the blood in consequence, will
traverse the vessels, when bent or doubled upon themselves,
as easily, as when they are distended in every
direction. For what reason should a different effect be
produced in the lungs, by the same disposition of the
parts?
2dly.—There are different vessels in the œconomy
which we may alternately bend or extend at pleasure:
such are those of the mesentery, when exposed by an
incision into the abdomen of the animal. Now in this
experiment, which has been already made to prove the
influence of the tortuous direction of the arteries upon the
mechanism of their pulsation, if one of the mesenteries
be opened, and then either bent or extended, in either
case the blood will be thrown out with the same degree
of violence, and in equal times will be emitted in equal
quantities. I have always obtained the same result in this
experiment which I have many times repeated. From
analogy we might expect the same from the vessels of
the lungs;[79] and from the following experiment it may be
proved.
3dly.—Take a dog, cut the trachea, and adapt the tube
of an injecting syringe to it, then make a vacuum in the
lungs, and cut the carotid artery. It is evident, that
according to the common belief, the circulation should
be immediately suspended, in this experiment, since the
pulmonary vessels from their ordinary state of distension,
must have passed to the greatest possible degree of collapse,
in consequence of the total abstraction of air;
notwithstanding which the blood will be violently thrown
out from the divided arteries for a certain time, and must
consequently traverse the lungs: it will afterwards cease
by degrees, but this, from causes which I shall explain
hereafter.
4thly.—The same effect may be produced by opening,
on both sides, the breast of a living animal, because the
warm and rarified air of the lungs, will be more than
balanced by the pressure of the colder air without;[80] now,
neither in this case does the circulation experience any
sudden change. For the sake of greater exactness, the
little air remaining in the cells of the organ may be
voided by a syringe.
Along with these observations let us place the facility
with which the pulmonary circulation continues to be
made, when collections of water, pus, or blood, are lying
within the pleura, or pericardium. In these cases the
air vessels are often prodigiously contracted, and consequently
the vessels of their parietes doubled and bent.[81]
If this state be taken into consideration, we shall have
sufficient data for concluding that the tortuous disposition
of the vessels, can never be an obstacle to the passage of
the blood; and therefore, that the interruption of the
mechanical functions of the lungs, can never directly put
a stop to the action of the heart, though it may do so
indirectly, in impeding the exercise of the chemical
functions of the lungs.
If then we can determine why the heart remains
inactive, when the latter phenomena are annihilated, we
shall have resolved a double question.
Many authors have asserted that the death, which
ensues after a too long continued inspiration, is owing to
the mechanical distension of the pulmonary vessels by
the rarified air, a distension impeding the circulation.
But this reason also is as false a one, as that which we
have already disproved. Inflate the lungs as powerfully
as may be, then tie the trachea and open the carotids, and
the blood will flow as impetuously as when the respiration
was perfectly free.[82]
According to Goodwyn, the reason why the contractions
of the heart are stopped, when the chemical functions
of the lungs have ceased to be performed, consists
in the want of that excitement which the red blood only
can produce upon the red-blooded ventricle. This ventricle,
says he, has not a sufficient stimulus in the black
blood, and death is occasioned because it no longer is
capable of transmitting any thing to the different organs.
In this case death must happen, as it would from ligature
of the aorta—precisely in the same way as when its
source is exclusively in the heart. The other parts die
only for want of blood, just as when in a machine, the
principal spring being taken away, the others cease to
act, because they are not put into action.
On the contrary, I am persuaded that there is a general
affection of all the parts, whenever the chemical functions
of the lungs are suspended; I am persuaded that the
black blood continues to be pushed on for some time by
the aorta, and that its influx into the organs is the occasion
of their death; that the organs die in fact, not
because they do not receive blood, but because they do
not receive red blood; in a word, that they are penetrated
by the material cause of their death; so much so, that
we may asphyxiate any isolated part at will, by injecting
it with venous blood while all the others shall continue
to receive the red blood of the heart. At present I shall
inquire into the phenomena of the contact of the black
blood with the parietes of the ventricle, and refer the
reader to the following chapters, for its effects upon the
other parts.
The movements of the heart may be stopped and made
to cease altogether from the influence of the venous blood
in two ways.—1st. As Goodwyn has said, because the
left ventricle is not excited by it upon its internal surface.—2dly.
Because such fluid, when carried into the
substance of the heart by the coronary vessels, must act
upon the muscular fibre of the heart in the same way as
it does upon the other muscles. Now, for my part, I am
assured that the black as well as the red blood, will excite
into contraction the internal surface of the aortic ventricle.
The following observations and experiments will confirm
my assertion.
1st. If asphyxia were to be followed by the consequences
which Goodwyn has supposed, it should influence
the heart in the first place; the annihilation of the functions
of the brain, as in syncope, should be only secondary;
nevertheless, asphyxiate an animal, by stopping up
the trachea, by placing him in a vacuum, by opening the
chest, or plunging him into carbonic acid gas, and it will
in every instance be observed, that his animal life is the
first to be interrupted, and that the creature externally is
dead; but that within the heart continues for some time
afterwards to act, and the pulse to be felt.
In this way the symptoms of asphyxia are not the
symptoms of syncope. In the latter the cardiac and
cerebral actions are suspended at the same instant, in the
former the heart survives, as in cases of strong concussion
of the brain for many seconds. It follows, that in
asphyxia, the different organs do not cease to act, because
the heart has ceased to supply them with blood, but
because it no longer supplies them with that sort of blood
by which they can be stimulated.
2dly. If the trachea of an animal be stopped, and an
artery opened, the colour of the blood which it emits,
will gradually be changed, and at last become as black as
that of venous blood. Now, notwithstanding this phenomenon,
which is as apparent as it can be, the fluid for
some time afterwards is thrown out full as strongly as it
would be, were it red. I have seen a quantity of black
blood discharged in this way, more than sufficient to kill
the creature from hæmorrhage; were it not already dead,
in consequence of its asphyxiated state.
3dly. In the last-mentioned experiment, it may, indeed,
be alleged, that some remains of air in the air cells,
might, as long as the black blood continued to flow, have
communicated to it a principle of excitement; but to put
it out of all doubt, that the venous blood does really pass
into the aortic ventricle, unaltered in its passage from the
corresponding cavity, the air may be entirely pumped out
of the lungs with a syringe, by exposing the trachea, in
the first place, and then adapting the instrument to the
transverse section of the tube; after this, let the carotid
be opened; now as soon as the red blood contained in
this artery is exhausted, the black blood will succeed to
it, and that, without undergoing a variety of gradations
in colour; in this case also for a time, the jet will be
very powerful, and only be gradually weakened; but if
the black blood were not an excitant to the heart, its
interruption should be immediate.
4thly. The following is another proof of the same
nature. Expose the breast on one side by sawing exactly
through the ribs before and behind: when this is done,
the lungs on that side will collapse. Proceed to open
one of the pulmonary veins; fill a syringe warmed to the
temperature of the human body with venous blood, then
push it into the red-blooded ventricle. Now, according
to the common opinion upon the subject of asphyxia, such
fluid should at least diminish in a sensible way, the
movement of that cavity, notwithstanding which, in four
successive experiments, I could not observe any such
diminution. On the contrary, in one of them, on pushing
the piston, the strokes of the heart were augmented
in number.
5thly. If the black blood be not an excitant to the
heart, it can only want such power, because it contains
more carbon and hydrogen, than the red blood;[83] but if
the heart of an animal, which has been killed expressly
for the experiment, by lesion of the brain or of the lungs,
has ceased to beat, it may, notwithstanding, be made to
contract as long as it preserves its irritability, by throwing
into the aortic ventricle either hydrogen gas, or
carbonic acid gas. It follows, that neither hydrogen gas
nor carbon can act as sedatives to the heart.
The experiments which I made and published last year,
on the emphysemata, produced in different animals with
these gases, have established the same truth with respect
to the muscles, since they do not cease to move in consequence
of such experiments, and after death, preserve
their irritability as they usually do.
Lastly. I have often succeeded in re-establishing the
contractions of the heart, which have been annihilated in
different sorts of violent death, by the injection of black
blood into the red-blooded cavities, with a syringe adapted
to one of the pulmonary veins.
Thus it is proved, that the red-blooded heart does
actually push the black blood into all parts of the body;
and in this way is the colour given to the different surfaces,
of which, in one of the following chapters, I shall
offer a sketch.
Neither does the simple presence of the black blood
act in a more sedative way upon the internal surfaces of
the arteries.[84] If, in fact, while the tube adapted to the
trachea is shut, the blood be made to flow from an artery of
the foot, it will be thrown out for some time, with the same
force which it would have been, were the pipe to be open.
The action, then, which it exercises in its passage from
the heart, upon the parietes of the arteries, does not
diminish the energy of these parietes. When this energy
decreases, it is at least in part from a different cause.
From the above experiments we may conclude, that
the black blood arriving in mass at the red-blooded ventricle,
and correspondent arterial system is able, from its
sole contact with them, to occasion the action of these
cavities; we may be equally certain, that were not the
functions of these parts suppressed from other causes, the
circulation would continue to be made in a very sensible
manner, at least, if not with force.
Of what nature, then, are the causes which interrupt
the circulation in the heart and arteries when they are
supplied with venous blood? for when this has been
flowing for some time, the jet of it is gradually weakened,
and ceases at last entirely; yet if the cock of the pipe be
opened, it will be restored with vigour.
I am persuaded that the black blood acts upon the heart
as it does on all the other parts, as we shall see that it
affects the brain—that it affects the voluntary muscles,
the membranes, and the system in general; the tissue of
which it penetrates and operates within it as a debilitant
upon each individual fibre. I am fully of opinion, that
the circulation would be almost as quickly interrupted as
in the preceding cases, were it even possible to supply
the coronary arteries of the heart with red blood, while
the black blood is transmitted to the various parts of the
body by the aortic auricle and ventricle.
The black blood operates by its contact with the fleshy
fibres, at the extremity of the arterial system and not by
its contact with the internal surface of the heart. Thus
it is only by little and little, and when each fibre has been
as it were injected, that the powers of such fibres diminish
and cease. On the contrary supposition, their cessation
and diminution should be almost sudden.
It may be demanded in what manner the black blood
acts at the extremities of the arteries, upon the fibres of
the different organs. Is it upon the fibres themselves, or
upon the nerves which are distributed to them? I am
rather inclined to suppose the latter to be the fact, and to
consider asphyxia as an effect produced in general by the
black blood upon the nerves, which every where accompany
the arteries of a certain diameter: for as we shall
presently see, the debility which in such case the heart
experiences, is only a particular symptom of a disease
in which the organs in general are the seat of a like
debility.
It might be demanded also in what way, that is to say,
by what manner of influence, the black blood acts upon
the nerves or fibres. Is it from the principles which it
actually contains, or from the absence of those which are
proper to the red blood? Is oxygen the principle of
irritability—are hydrogen and carbon the reverse?
These questions have been sufficiently disputed.—Let
us stop when we arrive at the limits of rigorous observation.
Now, I think, that we shall establish an assertion
the most strictly conformable with such principle, in saying
generally and without determining the manner, that
the heart ceases to act, when the chemical functions of the
lungs are interrupted, because the black blood with which
its fleshy fibres are penetrated, is not of a nature to keep
up their action.
From this manner of regarding the phenomena of
asphyxia with relation to the heart, it is evident that
both the ventricles should be equally affected by it, because
their parietes must be equally injected with venous
blood. Nevertheless, it is constantly observable, that
the movement of the red-blooded heart is the first to
stop; that the black-blooded heart in every case the ultimum
moriens; but this phenomenon does not suppose a
more real, a more decided debility in the one, than in the
other heart; for as Haller observes, the fact is common
to every kind of death in the red-blooded animal, and not
the case particularly in asphyxia.—Besides, were the red-blooded
heart the first to be absolutely affected, as the
theory of Goodwyn supposes, the following would be the
appearances on opening the asphyxiated subject.—1st. A
distension of the corresponding auricle and ventricle, by
the black blood which they would not be able to expel
into the aorta.—2dly. An equal fulness of the pulmonary
veins and lungs.—3dly. A consequent fulness and
swelling of the pulmonary artery and the black-blooded
cavities. In a word, the congestion of the blood should
be the greatest in that of its reservoirs, whose action is
the first to cease.
But this is contrary to observation—for 1st. In the
asphyxiated subject, the red-blooded cavities and pulmonary
veins, contain but a very small quantity of blood in
proportion to that which distends the opposite heart.
2dly. The place where the blood has stopped, is found
to be principally in the lungs, in the lungs must we begin
to follow its accumulation into the venous system. 3dly.
The arteries are as full of blood as their correspondent
ventricles, and consequently it cannot be in the ventricle
more than elsewhere, that death has been begun.
But what is the reason why the black-blooded heart is
the last to beat? because, says Haller, it is the longest
excited; because it contains a greater quantity of blood;
because the blood is sent into it from the largest veins
of the system, and regurgitates from the lungs. The
famous experiment is well known by which in emptying
the black-blooded cavities, and tying the aorta so as to
retain the blood within the red-blooded cavities, the contractions
of the latter are prolonged so much beyond the
contractions of the former. But in this experiment it is
manifestly the black blood which accumulates in the aortic
auricle and ventricle, because the breast must be preliminarily
opened, and therefore the lungs collapse.
Should a more direct proof be required, immediately
before the experiment, let the trachea be closed with a
syringe, and the air of the lungs be voided; the experiment
will just as well succeed; besides, the operator to
be sure of the colour of the blood in the aortic cavities,
has nothing more to do than to open them, as soon as he
has finished his experiment.
We shall conclude that the black blood is almost as
powerful a stimulus as the red blood to the inner surface
of those cavities, which usually contain the latter only:
the reason why they are the first to be arrested in their
action, is, because they do not receive so large a quantity
of blood as the others.
Notwithstanding what I have said, I do not entirely
reject the idea of the red-blooded ventricle being not
excitable by the black blood. It may indeed be less
excitable by this sort of blood, than by the other; but I
believe that the preceding considerations will reduce this
difference of excitement to a mere trifle.
The following, however, is an experiment where such
difference would appear to be very manifest. If a stop
cock be adapted to the trachea, and an artery opened, the
blood will blacken, and continue for some time to be
thrown out with its ordinary force, but at last the jet will
gradually grow weaker. If, after this, the air be admitted,
the blood will almost immediately become red and
its jet be visibly augmented. In this case the sudden
augmentation appears at first to depend upon the simple
contact of the red fluid with the sides of the aortic ventricle,
since it has not had the time to penetrate the tissue
of the heart; but let things be a little attentively examined,
and it will soon be seen that this impetuosity of
impulse, depends on the movements of inspiration and
expiration, to which the animal is obliged, on the admission
of air into the lungs. The heart excited at its
exterior, and perhaps a little compressed by these movements,
is the occasion of such phenomenon, and expels
the blood with a force which is far beyond that which
results from its habitual contractions.
What I have here advanced is proved, by the manifest
diminution of the jet, as soon as once the lungs have taken
on their accustomed degree of action. Besides, the influence
of a series of full expirations may be manifested
without dividing the trachea. Open the carotid and precipitate
the respiration of the animal by tormenting it
(for pain will constantly have this effect) and the jet of
blood will be visibly increased. The same augmentation
may be artificially produced, by suddenly compressing
the parietes of the thorax. These experiments succeed
best on animals already weakened by the loss of a certain
quantity of blood.
In the ordinary state of health however, a series of
strong expirations will not be found to quicken the pulse.
Of this I cannot assign the reason.
From what we have now said, it follows, that the
experiment, in which, on the opening of the cock of the
syringe, the blood is thrown out with augmented force,
is not so conclusive as might at first be imagined. I confess
that it embarrassed me much for many days, I hold
then my former conclusions to be good.
In the red and cold-blooded animals, the action of the
lungs has not so immediate a connexion with that of the
heart, as it has in the red and warm blooded animals.
I tied the lungs of two frogs at their basis, having
previously exposed them, by incisions made laterally into
the breast, the circulation however continued as usual for
a considerable time. After this experiment, I have seen
on opening the breast, the movements of the heart precipitated,
a circumstance depending no doubt upon its
contact with the air.
I shall finish this chapter by the examination of an
important question, and inquire into the reason, why when
the chemical functions of the lungs are stopped, the pulmonary
arteries, the black-blooded cavities of the heart,
and in a word all the venous system, are found so much
more full of blood, than the aortic system. In such case
the circulation appears at first to be interrupted in the
lungs, and then in the other parts, according to their
proximity to the lungs.
This phenomenon must have been observed by all
who have opened the asphyxiated subject. It has been
explained by Haller and others, from the tortuosity of
the vessels; but this opinion I have sufficiently refuted.[85]
But before I proceed to assign a more real cause, I
shall observe, that the lungs, (when the blood is first
arrested, because it finds in them the first obstacle to its
progress,) are found in a singularly various state, according
to the kind of death of which the individual has died.
In sudden, in instantaneous death, neither the lungs, nor
the black-blooded heart are very much distended.
I have observed this fact, 1st. In the bodies of two
persons who had hanged themselves and were brought
into my amphitheatre. 2dly. On two subjects who had
fallen into the fire, and were instantly suffocated. 3dly.
On dogs which I have suddenly drowned. 4thly. Upon
guinea-pigs, which I have killed in a vacuum, or in different
gases, or otherwise.
On the contrary, arrest the phenomena of respiration
in a gradual manner; drown the animal by plunging him
in water, and taking him out alternately, asphyxiate him
by placing him in a vessel of gas imperfectly closed, continue
as long as possible such state of pain and anguish,
and the lungs will be found extremely full of blood.
Between the extreme fulness, and the almost complete
emptiness of the pulmonary vessels, there is a variety of
degrees; now by the manner in which we kill the animal,
we can determine any one of these degrees at will: It is
in this way that we must explain that state of fulness in
the lungs of such subjects, as are usually brought into
our amphitheatres: in the greater number of cases, the
attacks of death are slow and gradual.
But whatever be the state of the lungs in the asphyxiated
subject, the venous system is full of black blood,
especially about the heart. In this respect, there is
always a very wide difference between the veins and the
arteries, and accordingly the blood must find in the lungs
the principal obstacle to its circulation: such obstacle, as
we have said, does not proceed from the tortuosity, and
state of collapse in the pulmonary vessels; its causes are
relative, first to the blood, secondly, to the lungs, thirdly
to the heart.
The principal cause depending on the blood, consists
in the great quantity of this fluid, which passes from the
arteries into the veins. In fact we shall soon see, that
the black blood when it circulates in the arteries, is not
capable of furnishing the materials of secretion, exhalation,
or nutrition, or if it be so, that it is not a stimulus
to the organs which are the agents of these functions.[86]
It follows as a necessary consequence, that the portion
of fluid which is usually taken up from the arterial system
by these different functions, flows on into the venous
system, together with the portion which should naturally
pass thither; hence there must be contained a greater
quantity than usual in the veins; and therefore a greater
difficulty be experienced in its passage through the lungs.
Practitioners in opening the bodies of asphyxiated persons,
have always remarked the abundance of blood
which is met with there. The fact has been particularly
remarked by Portal, and I have always found it in my
experiments.
The causes of obstacle to the passage of the blood proceeding
from the lungs, are first the non-excitement of
this organ by arterial blood. In asphyxia, the bronchial
arteries are penetrated by the black blood as well as the
rest. Hence its obscure and dusky colour in this case.
This colour and its successive shades, may be easily
remarked in the collapsed lung, when the chest is opened;
but in asphyxia, such blackness is principally owing
to the colour of the blood, contained in the pulmonary
veins.
The black blood when circulating in the bronchial
vessels, produces upon the lungs the same effect which it
does in the heart, by penetrating the coronary arteries;
it weakens the different parts—impedes their action, and
the capillary secretions which should be made there, from
the tonic powers of the organ.
The second cause of obstacle to the circulation, when
the chemical functions of the lungs are interrupted, is
the non-excitement of the organ by vital air. The first
effect of such air upon the mucous surfaces of the air-cells,
is to stimulate them, and so to keep them up in a
sort of perpetual erethism.[87] In the same way are the
powers of the stomach brought into action by the presence
of aliment there, and those of every reservoir of the
body, by the influx of their accustomed fluids. Again,
such excitement of the mucous surfaces by foreign substances
keeps up their tone. The privation of such
excitement, therefore, must put a stop to their capillary
secretions, which depend upon their tonic powers.
The different aeriform fluids which take the place of the
atmospheric air in the different sorts of asphyxia, appear
to act very differently upon the tonic powers, or the insensible
organic contractility of the lungs. Some of these put
a sudden stop to the circulation, others not. Compare
the asphyxiæ produced by nitrous or sulphurated hydrogen
gas, with those which may be occasioned by pure
hydrogen, or carbonic acid gas, and the difference will
instantly be seen. This difference indeed, as well as
the various other phenomena observable in the various
asphyxiæ, depends on causes which we have not mentioned,
but the affection of the air-cells, is evidently one
of them.
Lastly, the third cause of stagnation of the blood in
the venous vascular system, is that debility, which takes
place in the ventricle and auricle of this system, when
penetrated with venous blood: on the influx of the blood
from the cava, they are consequently distended, and this
is the case also with the cava itself, for the very same
reason. The causes which are now assigned, are sufficient
to shew why the black-blooded system, is gorged with
fluids in asphyxiæ.[88] The following considerations will
shew why the red-blooded system contains a lesser quantity
of fluid.
1st.—The obstacle commences in the lungs; therefore
the aortic heart must receive a less quantity than usual:
hence, as we have seen, proceeds the quicker cessation of
the contractions of this ventricle.
2dly.—The natural strength of the arteries, though
enfeebled by the influx of blood into their parietes, is
much superior to that of the veins, which besides are
subject to the same cause of debility.[89] Accordingly these
vessels and the aortic ventricle, are capable of surmounting
the resistance of the capillary vessels of the body in
general, much more easily than the veins and the venous
ventricle, are of vanquishing the capillaries of the lungs.
3dly.—In the general capillary system, there is only
one cause of want of action, viz. the presence of black
blood in it; to this in the lungs there is added another
cause, the want of that habitual excitement which this
organ receives on the part of the atmospheric air: accordingly
in the lungs, there is a greater resistance offered to
the influx of the blood, and with respect to the heart, a
less capability of surmounting such resistance. In the
other parts, the contrary of all this is observed, a less
resistance to the influx of the blood from the arteries into
the veins on the one hand, and on the other a greater
capability of overcoming such resistance.
4thly.—In the general capillary system, which is continued
on from that of the arteries, if the circulation be
embarrassed at first, in any organ in particular, it may
still continue to go on in the other organs, more or less,
in which case the blood regurgitates by these others into
the veins. On the contrary, as all the capillary system,
which is the continuation of the general venous system,
is concentrated in the lungs, the venous circulation must
be suppressed, whenever this organ loses its powers.
The preceding considerations, if I am not mistaken,
explain why the vascular systems are so unequally full
of blood after death, a circumstance, which is common to
almost every disease, as well as the asphyxiæ.
In the latter sort of death however, although the general
capillary system presents a less degree of resistance
than is made by the capillary system of the lungs, nevertheless
such resistance arising from the influx of the black
blood into the organs in general is very manifest, and
produces two remarkable phenomena.
The first is a greater quantity than usual of black blood
in the arteries, and therefore a greater difficulty of injecting
these vessels. Such blood is seldom coagulated.
Indeed in all cases the venous blood is much less coagulable
than arterial blood. This fact is proved, 1st, By
the experiments of modern Chemists. 2dly, By the
comparison of the blood of varices with that of aneurisms.
3dly, By the inspection of that which usually stagnates
after death in the veins of the neighbourhood of the heart.
The second circumstance, to which I have referred, is
the general livid colour of the greater number of the surfaces,
with the fulness of divers parts, such as the face, the
tongue and lips. These two phenomena indicate a stagnation
of the blood at the extremities of the arteries, in the
same way as they denote the same effect in the pulmonary
vessels; here there is a much more evident repletion,
because as I have said, the capillary system is there concentrated
within narrow limits.
The reflux of the blood of the veins towards the
extremities is the reason assigned by authors for the livid
appearance of asphyxiated persons. There is little reality
in this cause: in fact, this reflux, which is very sensible
in the trunks of the veins, diminishes continually towards
their ramifications, where it is impeded and rendered
impossible by the valves, besides which, the following
experiment is an evident proof, that we must attribute the
lividity in question, to the impulse of the black blood
from the aortic ventricle.
1st.—Adapt a syringe with its stop-cock to the divided
trachea. 2dly, Open the abdomen so as to distinguish
the intestines and epiploon. 3dly, Shut the cock. At the
end of two or three minutes, the red tint which animates
the peritoneum, and which is borrowed by this membrane
from the vessels, which creep underneath it, will be
changed into a dull brown colour. This colour may be
made to disappear and re-appear at will, by opening or
shutting the syringe.
Here we cannot, as if the experiment were made upon
other parts, suspect that a reflux is propagated from the
right ventricle towards the venous extremities, since
the mesenteric veins, together with the other branches of
the vena portæ, form a system apart, independent of the
great black-blooded system, and having no communication
with the cavities of the heart which correspond with
this system.
But I shall touch again upon this subject. The above
experiment is amply sufficient to prove, that the lividity
of the surfaces of the body is owing to arterial impulse.
At present we are in a condition to explain how the
lungs are more or less gorged with blood, more or less
livid, and how the livid spots upon the different parts
of the body are more or less marked accordingly as
the asphyxia has been more or less prolonged: for it is
evident, that if before death, the black blood have gone
round the two systems ten or twelve times, it will inject
the extremities much more than if it had made such circulation
only two or three times; at each revolution, a
greater or less quantity will be left in the extremities,
for want of action in the capillary vessels.
In finishing this chapter I shall take occasion to observe,
that the spleen is the only organ of the economy susceptible
like the lungs of assuming a very great variety of
volume. Scarcely is it ever found in the same state. It
has been falsely supposed that there is a relation between
the plenitude or vacuity of the stomach, and the inequalities
of the spleen; but this is not the case, as I have said
elsewhere. Such inequalities during the life of the body
do not exist, and supervene only at the instant of death.
It appears to me, that they depend especially upon the
state of the liver, the capillary vessels of which, are the
continuations of all the branches of the vena portæ as
the capillaries of the lungs are those of the great venous
system. Thus, when the hepatic capillaries from any
cause whatever are enfeebled, the spleen must swell and
be filled with the blood, which cannot traverse the liver.[90]
In such case, if I may so express myself, there is an
isolated asphyxia of the abdominal vascular apparatus.
The liver being to the spleen, what the lungs are to the
black-blooded cavities in common asphyxia. The resistance
is in the former, the stagnation in the latter. But
this matter may be better understood hereafter. Experiments
upon animals killed in different ways, would
throw much light upon it, and these I purpose undertaking.
By these means we may rigorously establish the
analogy existing between the stagnation of the blood in
the different branches of the vena portæ, and that which
is observed in the general venous system, in consequence
of various kinds of death. With respect to the spleen and
its system of veins, in ordinary asphyxia, I have never
remarked in it any peculiarity.
We have just seen, that in asphyxia, the movements
of the heart are paralyzed, because its fleshy fibres are
penetrated with venous blood. This fact should indicate
the same to be the case with reference to the action of the
brain. It is indubitably proved by experiment.
Whatever be the manner in which the pulmonary
functions are interrupted, it is always the interruption of
the chemical changes, which troubles the functions of the
brain.[91] What I have said upon this point with respect
to the heart, is exactly applicable to the cerebral mass: I
shall not repeat it. It remains to shew by experiment,
and the observation of diseases, that when the chemical
functions of the lungs are put a stop to, it is the black
blood which interrupts the action of the brain and that of
the nervous system. In the first place let us examine our
experiments.
I first began by transfusing into the brain of an animal,
the arterial blood of another, that this essay might serve
as a point of comparison for others. Open one of the
carotids of a dog; tie the extremity towards the brain,
and fasten a tube to that which is next the heart; then
open the carotid of another dog, tie the extremity of the
vessel next the heart, and fix the other end of the tube
into that which is next the brain; then let the assistant,
who meanwhile should have had his fingers upon the
artery of the first dog underneath the tube, remove his
compression, and the carotid of the second dog will be
seen beating under the impulse of the blood injected from
the heart of the first. This operation fatigues but little
the animal which receives the blood, particularly if one
of the veins be previously opened, to prevent too great a
fulness of the vessels. It will live very well afterwards.
This experiment has been often repeated, and always
with the same results.
After this experiment, I opened the carotid, and the
jugular vein of another dog, and after tying the extremity
of the carotid next the heart, received the blood of the
jugular into a warm syringe, and injected it into the
brain. The creature appeared immediately to be agitated,
breathed quickly, and seemed to be in a state of suffocation,
similar to that of asphyxia. Its animal life became
entirely extinct; the heart, however, continued to beat,
and the circulation to go on for half an hour afterwards;
at the end of which time the organic life was terminated
also.
This dog was of a middle size, and about six ounces of
blood were injected with a gentle impulse, for fear of that
being attributed to the shock, which ought to have been
the result of the nature and composition of the fluid. I
repeated this experiment upon three dogs the same day,
and afterwards at different times upon others; the result
was invariable, not only as to the asphyxia of the animal,
but even as to the concomitant appearances.
It might be thought that out of its vessels, and exposed
to the contact of the air, the blood might imbibe a pernicious
principle, or be deprived of that which is requisite
for the maintenance of life. It might be imagined, that
to this cause was owing the sudden death of the dog, on
the injection of the brain with venous blood. To shew
that this was not the case, I made a small opening in the
jugular of a dog, to which I adapted a moderately warm
syringe, and pumped the blood immediately from the
vein.—It was afterwards thrown into the carotid: the
symptoms were the same as the preceding, but less marked,
and the death of the creature induced more slowly.—It
is probable, then, that the air when in contact with the
living blood without its vessels may alter it a little, but
the essential cause of death is still the same.
Hence it appears that the black blood either is not an
excitant capable of keeping up the cerebral action, or that
it acts in a deleterious manner, upon the brain. The
injection by the carotid of various other substances will
produce analogous effects.
I have killed animals in this way with ink, oil, wine,
and water coloured with indigo. The greater number of
the excrementitious fluids, such as urine, bile, the mucus
of catarrhs, occasion death also by their simple presence
on the brain. The serosity of the blood is fatal, but not
as quickly so. Now it is certainly upon the substance of
the brain, and not upon the internal surface of the arteries,
that these different substances exert their influence. I
have injected them all into the crural artery. In this
way they are none of them mortal, but occasion always
a torpor, amounting even to paralysis at times.[92]
The black blood is doubtless fatal to the brain, the brain
becoming at once a tonic from its presence. In what way
does it act? I do not pretend to determine the manner;
for this were only to begin a series of conjectures.
By this time we are authorised to conclude, that in
asphyxiæ, the circulation which continues for some time
after the interruption of the chemical functions of the
lungs, interrupts the cerebral functions, from its being
composed of black blood only. The fact is proved in
another manner, for the movements of the brain continue
to be made as usual.
If the cerebral mass be exposed, and the creature
asphyxiated, the animal life will be extinguished, but the
motion of the brain will be apparent still. Since then the
latter cause of life subsists, the cause of death must be in
the nature of the fluid, by which the organ is penetrated.
Nevertheless, if any affection of the brain coincide with
asphyxia, the death which is occasioned by the latter,
will be quicker than is usually the case. Strike a dog a
violent blow upon the head, and then if he be deprived of
air, he will die on the instant. In asphyxiating another
animal already in a state of stupor, from compression of
the brain, I observed that the vital functions were interrupted
somewhat sooner, than when the brain is untouched
during that operation; but the consequences hitherto
deduced, may be supported by other experiments.
If in asphyxia the black blood suspend the action of the
cerebral mass, it is evident that the black blood taken
from the arteries of an animal dying of asphyxia, and
injected into the brain of another, will be the cause of
death.
The experiment will be found to succeed—cut the
trachea, of a dog, and tie it up hermetically; then in the
course of two or three minutes, open the carotid and
receive into a syringe the blood, which flows from the
vessels; inject it into the brain of another animal, and it
will die.
The following experiment is very similar, but offers a
somewhat different result. 1st. Adapt a tube with a stop-cock
to the trachea of a dog, and a tube of silver to the
carotid, next the head, after dividing this vessel, and tie
up the extremity towards the heart. 2dly. Fix the other
end of the tube to the divided carotid of another dog next
the heart, and tie the extremity of the vessel towards
the head. 3dly. Shut the cock of the tube in the trachea,
and the black blood of the one dog in a short time, will
be injected into the brain of the other.
The appearances above described will shortly afterwards
succeed, but not so soon as in the former experiment,
and if the transfusion be stopped, the animal which
has been asphyxiated in this way, may recover and live.
In the preceding experiment he will always die. It
appears then that some extraneous pernicious principle is
imbibed by the venous blood, when in contact with the
air. Observe that for the latter experiment the dog from
which the brain of the other is to be injected, must be
stronger and more vigorous than the other. The reasons
are evident.
I was desirous of trying whether the venous blood
would not be capable of keeping up the cerebral action,
if reddened artificially. For this purpose I opened the
jugular and the carotid of a dog, and received the blood
of the vein in a vessel filled with oxygen; it immediately
became of a vivid purple, but on its injection into the
brain, the animal was very suddenly killed. I was much
surprised at this result, but ceased to be so on remarking,
that a great quantity of air was mixed with the fluid,
and that it arrived upon the brain, in a state of foam:
now we know that a very small number of bubbles are
sufficient to kill an animal, whether they be introduced
on the side of the brain, or on that of the heart.
From this reflection, I was induced to repeat my experiments
upon the injection of black blood, suspecting as
I did that some small quantity of air might in these cases
have been contained in the extremity of my syringe. I
soon however recollected that if this cause were real, it
should produce the same effect in every instance whatever
were the fluid employed, now when water is injected
there is nothing of the kind observable.
We may be thus assured that the black blood is either
incapable of keeping up the action of the brain, or that
it acts in a deleterious manner upon that organ, from the
very nature of the principles, which it contains. From
such datum it should appear that the life of the asphyxiated
person might be restored, by pushing on into the
brain a sufficient quantity of arterial blood, but here we
must make a distinction of two periods in asphyxia: 1st.
That in which the cerebral functions are only suspended:
2dly. That in which the circulation and the movements
of the breast are stopped (for this disease is ever characterised
by the sudden loss of all animal life, and consecutively
by that of the organic life.) Now, as long as
the first period of asphyxia continues, I have observed
that, by the transfusion of red blood into the brain, from
the heart of another animal, the movement of the creature
which is dying will be restored by degrees, and the
cerebral functions resume in part their activity; but this
is only a temporary thing, and the animal will fall again
into its previous dying state, if the asphyxiating cause be
continued.
On the other hand, if during the first period, to which
we have alluded, the air be readmitted, into the trachea,
the lungs will be reanimated, the blood be coloured, and
the creature be revived without the assistance of any
transfusion; and such transfusion again is of no avail,
after the second period of asphyxia, so that this experiment
offers only a proof of what we already know; with
respect to the difference of the influence of arterial and
venous blood upon the brain, and not a remedy in case
of asphyxia.
Again, whenever I have injected venous blood into
the brain, by the help of a syringe, I have universally
found that such proceeding is fatal. Though the cause of
asphyxia be removed, and arterial blood injected, either
with the syringe, or immediately from the heart of another
animal, it is of little effect, and frequently of none whatever.
And in general asphyxia when produced by blood,
which has been taken from the venous system itself and
pushed into the brain is much more certain and more
decided, than that which is occasioned by ligature of the
trachea, or the introduction of different gases into the
lungs.
After having established by different experiments, how
fatal the influence of the black blood is upon the brain,
which receives it from the arteries whenever the chemical
functions of the lungs are suspended, it will not be amiss
or out of place to shew, that the phenomena of the
asphyxia, which are observed in the human subject,
accord with the experiments of which I have given the
detail.
1st. It is generally known that every kind of asphyxia
affects the brain in the first instance; that the functions
of this organ are the first to be annihilated; that the
animal life, and particularly the sensations cease; that all
our relations with exterior objects are instantly suspended,
and that the organic functions are only consecutively
interrupted. Whatever be the mode of asphyxia, by
submersion, strangulation, gases, or a vacuum, the same
phenomena occur at all times.
2dly. It is known that the greater number of those
who have escaped suffocation, have been sensible only of
a general stupor, the seat of which has been evidently in
the brain. It is known also, that death is almost always
certain in these cases, while the pulse and the heart have
ceased to be felt.
3dly. It is affirmed by almost all such persons as have
survived this accident, especially when caused by the
vapour of charcoal, that the first thing of which they
were sensible, was more or less pain, in the head, an effect
in all probability occasioned by the first influx of the
black blood into the brain. This fact has been noted by
the greater number of authors, who have written on
asphyxia.
4thly. The vulgar expression that “charcoal flies to
the head” is surely a proof that the brain, and not the
heart, is the first affected in the asphyxia occasioned by
this deleterious substance. The unprejudiced vulgar,
oftentimes observe more correctly than we do, who frequently
see only what we wish to see.[93]
5thly. There are many examples of persons, who after
escaping the pernicious effects of the vapour of charcoal,
have been subject afterwards to paralytic affections, and
loss of memory. Such changes have evidently their seat
in the brain. Convulsion also is frequently the effect of
the impression of mephitic vapour: head-ache is a common
symptom, and for the most part remains after the
others have disappeared. In every book of cases may
be seen examples of these affections.
In cold-blooded animals, and in reptiles especially, this
influence of the black blood on the brain, though real, is
much less apparent. Make an incision into both sides
of the breast of a frog, then tie the lungs at their root,
and the animal will live notwithstanding for a considerable
time. Cut away the lungs entirely, and the same
phenomenon will be remarked. In fish, the relation
between the lungs and the brain, is somewhat more
direct, for by the organization of the branchiæ, they
differ essentially from reptiles. I have taken away the
cartilaginous plate which covers the gills of the carp,
the motion of the gills however continued to be made as
before, and the animal lived without any apparent injury
done to its functions. I afterwards put a ligature about
the cartilaginous rings which sustain the branchiæ, so as
to hinder all motion in the pulmonary apparatus. The
effect was, that the animal languished, his fins dropt,
his muscular movements soon grew weak, then ceased
entirely, and the creature in the course of a quarter of an
hour was dead. The same phenomena with some little
variety, were observable in a carp from which I cut away
the branchiæ.
After all however, the particular nature of those relations,
which unite the heart, the lungs, and the brain,
both in the red and cold-blooded animals, is well worthy
the farther investigation of physiologists. The latter sort
of animals, can neither be subject to syncope or apoplexy,
or at least the character of these diseases must be
very much modified in them. They are with much more
difficulty asphyxiated. We shall now return to those
species which bear a nearer resemblance to man.
From the influence of the black blood over the heart,
the brain, and the rest of the organs, it was my opinion,
that persons affected with varicose aneurisms, would
perish less quickly from asphyxia then others; because
the red blood passes into the veins, and traverses the lungs
without requiring alteration. Accordingly, it should be
capable of keeping up the cerebral action.
To be assured if this suspicion were well founded, I
made a communication between the carotid artery and
jugular vein of a dog, by means of a curved tube. The
pulsation of the artery was thus communicated to the
vein. I afterwards asphyxiated the animal by stopping
the trachea, but the phenomena of death were little different
from those of common asphyxia.
We may conclude with certainty, from the various
considerations and experiments presented in the present
chapter.
1st. That when the chemical phenomena of the lungs
are interrupted, the black blood acts upon the brain, as it
does upon the heart, by penetrating the tissue of that
organ, and depriving it of the excitement, which is necessary
to its action.
2dly. That its influence is much more rapid upon the
first, than on the second of these organs.
3dly. That it is the inequality of such influence, which
occasions the difference in the cessation of the two lives
in the case of asphyxia. The animal life is always annihilated
before the organic life.
We may conceive from what has been said in this and
the preceding chapter, how unfounded are the suspicions
of those who have supposed that the brain, after the separation
of the head from the body by the guillotine, might
live awhile and have sensation. The action of this organ
is immediately connected with its double excitements.—1st,
By motion; 2dly, By the nature of the blood which
it receives. Now, when the interruption of such excitement
is sudden, the interruption of every kind of feeling
must also be sudden.
When the chemical functions of the lungs are suspended,
the disturbance induced in the functions of the brain,
has indeed a very considerable influence on the death of
the other organs; nevertheless, such disturbance is the
beginning of death only in the animal life, and even then
is connected with other causes. The organic life ceases
from the sole presence of the black blood among the different
organs. The death of the brain is only an isolated
and partial phenomenon of asphyxia, which does not take
place in any particular organ, but in all alike. We shall
explain this assertion in the following chapter.
I have just shewn in what way the interruption of the
chemical phenomena which take place in the lungs, annihilates
the functions of the heart and brain. It remains
me to shew, that the other organs of the body are as much
affected by such cessation; so that asphyxia, as I have
said, is a general disease, and not an affection of any one
organ in particular.
But before I proceed to analyze the effects of asphyxia
upon the organs in general, and consequently the mode of
action of the black blood upon them, it may be of use to
explain the phenomena of the production of this kind of
blood, at the instant when the functions of the lungs are
suspended. This paragraph will possess, perhaps, some
interest; it might have belonged indifferently to either of
the preceding chapters.
It is known in general, that the blood is coloured in
traversing the lungs, that from black it becomes red; but
this very interesting fact, has not been hitherto the object
of any precise or rigorous experiment. The lungs of the
frog, of which the air vessels are large, and the membranes
thin and transparent, would serve very well for
the purpose of observing the process of the phenomenon
in question, but for the slowness of respiration in these
animals, the difference of organization in their lungs, and
the too small quantity of blood by which they are traversed.
On such account there can be little analogy between
them and the more perfect animals, and then again our
experiments upon these little amphibiæ, are all of them
rendered incomplete, by the tenuity of their pulmonary
vessels, and the impossibility of observing the correspondence
of the change of velocity in the circulation, with the
colour of their blood.
The phenomena of the respiration of man, and those of
the functions which are dependent on it, can be illustrated
only by experiments made upon animals with a double
ventricle, with a complete pulmonary apparatus, possessed
of a temperature superior to that of the atmosphere, and
the two separate systems of venous and arterial blood;
but on the other hand, in the mammalia resembling man,
their respiratory apparatus, the thickness of the vessels
and cavities of the heart, impede the view of the blood
which they contain; and experiments made without an
absolute inspection of the fluid there, can only give us
approximations. The indecisive experiments of former
physiologists on this subject were my motives for the
present inquiry.
One of the best methods of judging of the colour of the
blood, consists as I have often said, in fixing a tube with
a stop-cock to the trachea. By this, the influx of air into
the lungs, may be regulated or altogether stopped. By
this, we may distend the organ, or entirely evacuate it;
it gives us also the facility of introducing whatever gas
we please. The animal breathes very well by such pipe
when it is open, and would live with it for a considerable
length of time without any very great alteration in its
functions.
In the second place, an artery, the crural or carotid for
instance, must be opened with the view of observing the
varieties of colour in the blood projected from it. A
small artery should not be chosen. From such a one the
course of the blood would be suspended by the slightest
accident; and on the other hand, the larger arteries
expend in a little time too large a quantity of blood; this
inconvenience may be remedied, by adapting to these
vessels a tube of a small diameter, or a stop-cock.
All things being thus prepared, on a dog, for instance,
let us see what are the phenomena which take place, when
the colour of the blood is altered. In my indication
of these, however, I shall speak only of what I have
seen, and by no means pretend that in man their duration
should be similar or uniform, or even that in animals
of the same species, under the different circumstances of
sleep, digestion, exercise, and passion, &c. if it were
possible in such way to repeat them, they should be alike.
The instability of the animal functions, as I have said, is
extreme; they cannot be submitted to calculation; they
remain indeed the same, but their variations as to plus or
minus are innumerable.
Let us now return to our subject:
1st. If the cock of the pipe be shut immediately after
the animal has inspired, the blood begins to be altered in
colour at the end of about thirty seconds.—At the end
of a minute its colour is dark; at the end of a minute
and half or two minutes, it is perfectly similar to venous
blood.
2dly. If the cock of the pipe be shut immediately after
the animal has expired strongly, the blood receives its
tinge of black some seconds the sooner.
3dly. If the air of the lungs be pumped out entirely
with a syringe, the blood will suddenly pass from red to
black.[94] In such case it appears that the artery immediately
throws out a black stream, after it has expelled the
red blood which it previously contained. There is no
gradation. The blood is expelled by the arteries, such as
it is in the veins.
4thly. If, instead of making a vacuum in the lungs,
we inflate the air cells to the full, the blood is a longer
time in becoming black, a minute at least, and is not completely
black before the end of three minutes.—This will
vary according to the quantity of air injected.
From all these experiments it follows, 1st, That the
length of the interval, during which the blood retains
its red colour, is in direct proportion to the quantity of
air contained in the lungs; 2dly, That as long as there
remains any quantity however small of respirable air in
the cells of the lungs, the blood will preserve more or
less of its crimson colour; 3dly, That this colour diminishes
in proportion as the respirable air diminishes; and
4thly, That the blood is exactly similar to that of the
veins, as soon as the whole of the vital air in the extremities
of the bronchiæ has been exhausted.
In my different experiments with regard to asphyxia,
I have remarked, that if after shutting the cock of the
syringe, the animal agitate the chest by similar movements
to those of inspiration and expiration, the blood
is a longer time in losing its red colour, than in the case
where the breast remains at rest. Such motion and
agitation must cause a circulation of air in the cells, in
consequence of which, a greater number of its points
must be presented to the circulating fluid. My experiments
which I shall presently detail on the breathing of
animals in bladders, will prove the truth of the above
explanation.
At present I pass to a contrary set of phenomena—to
those which are exemplified when the blood regains its
arterial colour during the period, which, from a state of
asphyxia, restores the animal to life.
1st. When the cock, which for some minutes has been
shut, is opened, the air immediately penetrates into the
bronchiæ; but previously the animal expires strongly.
Six or seven large inspirations and expirations follow
each other precipitately. The artery being now examined,
a jet of a very vivid colour is seen succeeding to the
efflux of black blood, and takes place in thirty seconds at
most, from the time of opening the tube. This is the
inverse of the phenomenon above described. There are
no successive shades perceived from black to red; the
passage is instantaneous. The brightness of the colour
seems even to be greater than is natural.
2dly. If instead of suddenly turning the cock, a very
strong stream of air only be admitted, the colour is less
lively indeed, but just as quickly regained.
3dly. If there be adapted to the stop-cock a syringe
full of air, and this fluid be pushed into the lungs, on
opening the pipe, and then the pipe be suddenly shut
again, the blood will become red, but much less evidently
so, than when the entrance of the air is owing to voluntary
inspiration. Here the portion of air injected must
repel into the bottom of the cells whatever is already
vitiated, while on the contrary, if the tube be simply
opened, the vitiated air is at once rejected, and then
replaced from without. The following experiment appears
to confirm this idea.
4thly. If instead of pushing air upon that which is contained
in the lungs, we pump out the vitiated air in the
first place, and then inflate the organ, the colouring process
will be more rapid, and the colour of the blood
itself especially, more lively than in the preceding case,
though less so than in the first of this latter suite of experiments.
5thly. The lungs being exposed on both sides by a
lateral section of the ribs, the circulation will continue to
go on for a certain time. Now, if by means of a syringe
adapted to the stop-cock in the trachea, the pulmonary
vesicles be alternately emptied and dilated, the changes
from red to black, and from black to red, will be observed
as in the above experiment, as long as the circulation
lasts.
The following consequences may be inferred from the
facts, which I have mentioned.
1st. The rapidity with which the blood becomes red
again, on opening the pipe in the trachea, is a plain proof,
that the principle from which this colour is gained, must
pass into the blood across the membranous parietes of the
air cells, and not by means of the absorbents. I shall
establish this fact hereafter upon other proofs.
2dly. The celebrated experiment of Hook, in which
the enfeebled movements of the hearts of animals in a
state of asphyxia are accelerated by injecting air into the
lungs, is very well explained. The red blood penetrates
into the fibres of the heart, and puts an end to the debility
induced, by the influx thither of the black blood.
3dly. I do not believe, that motion can ever be restored
to the heart, when once it has been wholly annihilated
by the presence of venous blood. In this I have never
succeeded, though I have often attempted it. Many
authors, however, pretend to have done so. If the heart
be reanimated by arterial blood, it is necessary at any
rate, that such blood, should pass into it, now in what
way can it arrive there, if the circulation have entirely
ceased.
We must observe, however, that there are two cases
of interruption in the action of the heart from asphyxia.
Sometimes there supervenes a syncope which arrests the
movement of this organ, before the black blood has been
able to produce such effect; and here it is manifestly
capable of excitement, from the presence of the red blood,
just as it is from the application of any irritating cause;
but when it has been injected with venous blood, it then
contains within itself the principle of its inertia, which
can be removed only by the contact of arterial blood with
it; but such contact is become impossible.
I was very desirous of knowing what the influence
might be of the different gases when inspired upon the
colour of the blood. Accordingly I successively adapted
to the pipe different bladders, containing hydrogen and
carbonic acid gas.
The animal alternately swells and contracts the bladder
by the different motions of the thorax. It is calm at first,
but at the end of three minutes, begins to be agitated; its
respiration is now hurried and embarrassed, and at the
end of four or five minutes, the blood of the carotid is
black.
Whichever of the two gases be employed, there is little
difference in the above phenomena. This remark should
be compared with those of the Members of the Institute,
who have assured us that complete asphyxia supervenes
only after an interval of ten minutes, with pure hydrogen,
and at the end of two minutes with carbonic acid gas.
The black blood must continue, therefore, to circulate for
a longer time in one than in the other kind of asphyxia
here spoken of. This circumstance confirms some reflections
which I shall have occasion to offer upon the difference
of asphyxiæ.
For what reason should the blood be a longer time in
losing its colour, when bladders of non-respirable air are
fixed to the pipe, than when the cock is simply turned?
The reason of this is evident. By the different motions
of the lungs, the air is expelled and reabsorbed, the respirable
portion of it must consequently be successively
presented to the capillary orifices, by which it is transmitted
to the blood.
On the contrary, when the pipe is simply shut, the air
it is plain has not the same influx and efflux; in comparison
with such motion, it may be said to stagnate so that
the respirable portion of that which is enclosed in the
bronchial cells is exhausted, and the blood ceases to be
coloured, though there remain in the trachea and its larger
divisions, a considerable quantity of fluid, which has not
been despoiled of its vivifying principle. Of this we
may be certain, after the death of the animal, by cutting
the trachea under the pipe, and plunging a bougie into
it. The process by which the blood gains its red colour
appears to take place only at the extremities of the
bronchiæ, the inner surface of the larger aerial vessels,
has nothing to do with this phenomenon.
We may convince ourselves of the reality of the explanation
which I have offered, if we pump out the air of
the lungs, before we fit the bladder to the trachea; for in
such case, the animal must breathe the air of the bladder
without mixture. Here the change of the blood to black
is almost sudden, but here also, as in the preceding experiment,
there is little difference in the phenomena, whatever
gas we employ. I have chosen the two gases above mentioned,
because they enter into the phenomena of natural
respiration.
When we adapt to the pipe a bladder full of pure
oxygen, the blood is very long in becoming black, but
does not at first assume a redder tint than it usually has.
We have just established what are the phenomena of
the alteration of colour in the blood, when the chemical
functions of the lungs are suspended. Before we consider
the influence of this change upon the death of the organs,
let us prove, that they are really penetrated by the blood
when so altered.
I have proved it to be a fact, that the force of the heart
subsists for some time, notwithstanding the influx of the
black blood into it, and have shewn that the black blood
is thrown out with a jet, similar to that of the red blood,
&c. &c. Hence I might already conclude, 1st, That the
arterial circulation continues for a certain time, though
the arteries contain a fluid, to which they are not accustomed,
and 2dly, That the necessary consequence of such
circulation, must be the injection of the different parts of
the body with black blood; but we shall deduce the latter
conclusion from precise and rigorous experiments. To
be certain of this important fact, we have only to expose
successively the different organs, while the animal is suffering
a death of asphyxia. I have in this way examined
the muscles, the nerves, the membranes and the viscera.
The following are the results of my observations.
1st. The colouring matter of the muscles, exists in the
body in two states—at liberty, or in a state of combination;
in the vessels, where it circulates with the blood,
or in the fibres, with which it is combined. It forms
especially the colour of the muscles, and in such state
undergoes no alteration from asphyxia; in its free state
it is blackened. The divided muscles furnish an infinity
of black drops, which are no other than indices of the
divided vessels. Such drops contrast with the red of
the muscles; but when circulating within them, are the
cause of that livid tint which they then present.
2dly. The nerves are habitually penetrated by a number
of small arteries, which creep along within their tissue,
and carry to them both excitement and life. In the state
of asphyxia the black blood by which they are traversed,
is announced by the dull brown, which succeeds to the
rosy-white, which is natural to them.
3dly. There are few parts, where the influx of the black
blood is more visible, than in the skin; the livid spots so
frequent in asphyxia, are only the effect of the obstacles
which it meets with, in its passage towards the general
capillary system, to the organic contractility of which it
is not a sufficient excitant. To this cause also is owing
the tumefaction of certain parts, such as the cheeks and
lips. This phenomenon we have seen already in the
lungs, they cannot be traversed by the blood and therefore
become in the last moments of life, the seat of a fulness,
which affects the whole of the capillary system there; but
for the reasons, which I have assigned, such fulness is
always more evident in the capillary system of the lungs,
than in that of the system in general.
4thly. The mucous membranes also, when the chemical
functions of the lungs are interrupted, exemplify a
similar phenomenon. The swelling of the tongue, observable
in those that have been drowned or hanged, or
asphyxiated by the vapour of charcoal, the lividity of
the membrane of the mouth, of the intestines, and the
bronchiæ which have also been remarked, depend on
no other cause. The following is a proof of this assertion:
Drag out of an animal a portion of the alimentary canal
and divide it in such way as to expose its inner surface.
Then shut up the pipe which has been previously adapted
to the trachea, and at the end of four or five minutes, a
brown tint will succeed to the red one, which is natural
to this surface.
5thly. I have made the same remark upon the fleshy
granulations of a wound, inflicted on an animal, for the
purpose of observing the manner in which they are coloured
by the black blood. In the two last experiments, this
phenomenon is slower in taking place than in many other
circumstances.
6thly. The alteration of colour in the serous membranes
is much more quickly effected than it is in the
mucous membranes. Of this we may assure ourselves by
comparatively examining the outer and inner surfaces of
the intestines, while the pipe in the trachea is shut; in
the serous membranes, the livid tint which they assume,
depends upon the vessels, which creep underneath them,
and not on the blood by which they are penetrated.
Now as these vessels are considerable, the black blood
must flow into them almost as soon as it is produced.
In the mucous membranes on the contrary, and in all
cicatrices, the colour which they take on in asphyxia, is
made by the capillary system of the membrane itself,
which system is much more tardy than the other, to
receive the black blood, and to be penetrated by it; so
much so indeed, as to refuse it in some parts. I have
many times seen the membrane of the nasal fossæ very
red in asphyxiated animals, while that of the mouth has
been quite livid, for there are parts into which as I have
said the black blood will not penetrate at all, and then
they preserve their natural colour. 2dly. There are
others into which it evidently passes, but where it stops,
and then a simple change of colour is observed, if it have
penetrated but in small quantity; and again, if it have
penetrated in a considerable quantity, together with such
change of colour, there will be observed a tumefaction of
the part. 3dly. In other cases, the black blood merely
traverses the parts, without stopping in the capillary
system, and passes at once into the veins, as the red blood
does.
In the first and second case, the general circulation
experiences an obstacle which puts a stop to it in the
general capillary system. In the third, which is much
more universal, it is in the capillaries of the lungs that
the blood is at last arrested, after having circulated in the
veins.
These two sorts of impediment coincide with each
other, in many instances. Thus in asphyxia, a part of
the black blood which circulates in the arteries stops
in the face, upon the mucous surfaces, in the tongue, and
in the lips, while the other, and much the larger quantity,
finds no impediment in the general capillary system, and
is finally arrested in the lungs.
What is the reason, why certain parts of the capillary
system refuse to admit the venous blood, or if they admit
it, do not pass it on to the veins; while others are less
enfeebled by it, and transmit it as freely as ever. All
this must certainly depend on the relation existing between
the sensibility of each part and the venous blood.
I was desirous of making use of the power, which we
possess, of changing the colour of the blood, for getting
some insight into the influence of the circulation of the
mother, upon that of the fœtus; accordingly I procured
a bitch big with young, and asphyxiated her, by closing a
tube, adapted to the trachea. About four minutes after
she had ceased to breathe, I opened her; the circulation
was going on. I then cut into the matrix, and exposed
the cord of two or three of the fœtuses. The artery and
the vein, were both of them full alike of venous blood.
Had I been able to procure other bitches in a similar
state, I should have repeated this experiment in another
manner. I should in the first place have compared the
natural colour of the vein, with that of the artery. In
many of the young of the guinea pig, the difference
appeared to me to be much less than it is in the adult
animal. In many circumstances indeed I could perceive
no difference whatever. Both the arterial and venous
blood were equally black, though the respiration of the
mother was in no wise impeded by the opening of the belly.
Secondly, I should have closed the tube in the trachea, and
then have observed whether the change in colour of the
umbilical artery of the fœtus (supposing the blood of the
artery to be different from that of the vein) were correspondent
with that, which would inevitably take place in
the blood of the mother. Experiments made with a
view to these circumstances, and on large animals, might
probably throw much light upon the mode of communication,
between the mother and the fœtus. Observations
are also much to be desired, with respect to the colour of
the blood in the human fœtus, and the cause of its passage
from a livid colour, to the very marked red which it
assumes, some little time after birth.[95]
I might add a number of examples to these, which I
have already related of the blackening of the organs by
the venous blood. Thus, the kidney of a dog exposed,
while the animal is dying of asphyxia, is much more
livid than in its natural state, the spleen also and the liver,
when divided, emit only black blood, instead of that
mixture of red and black blood which is observable, in
the section of these organs, upon an animal which breathes
freely.
But I trust that we have facts enough to establish it as
a certainty, 1st, That the black blood after the interruption
of the chemical functions of the lungs, continues for
some time to circulate, and 2dly, That it penetrates into
the organs, where it replaces the red blood; these circumstances
explain the reason, why on opening the body we
always meet with black blood even in the vessels which
are destined for the circulation of arterial blood.
In the last moments of existence of whatever death
the individual may have died, we shall always observe the
lungs become embarrassed and cease to perform their
office, for some time previous to the total suspension of
the functions of the heart. The blood makes its circle
through the system, after ceasing to receive the influence
of the air, and consequently in its venous state; accordingly
it must remain so in the organ in every case, although
the circulation be much less evident, than in asphyxia, for
it is in this circumstance that consists, the great peculiarity
of asphyxia. The following phenomena may now be
easily understood.
1st. When the left auricle and ventricle together with
the large divisions of the aorta, on opening the body,
are found to contain blood, such blood is always black.
The fact is familiar to those who are in the habit of
dissecting. In exercising my pupils on the surgical operations,
I have always observed that when the open arteries
are not entirely empty, their contents are composed of
venous blood.
2dly, The corpus cavernosum is always gorged with
this sort of fluid, whether flaccid or in a state of erection.
For I have seen it in the latter state in two subjects
brought to my amphitheatre. One of these men had
hanged himself, the other had died of concussion of the
brain.
3dly, The blood which is found in the spleen is never
red; but sometimes on the exterior, and sometimes on
the concave surface of this organ, I have observed spots
of a scarlet colour, for which I cannot account.
4thly, After death, the mucous membranes lose the
red colour by which they are characterized during life.
They assume a black and livid hue.
5thly, Blood extravasated in the brain of persons in a
state of apoplexy, is almost always found to be black.
6thly, Sometimes, instead of accumulating inwardly
the blood injects the surface of the body. In such case
the face, the neck, and shoulders swell, and are infiltrated
with blood. I have frequently remarked this sort of
phenomenon in the subject, but have never found it coincide
with any internal extravasion.—The colour of the
skin is then of a purple or deep brown, an evident sign
of the sort of blood with which it is injected, and is
evidently produced by the stagnation of the black blood
in the external capillary system, not by the reflux of the
blood from the veins.
I shall not dwell any longer upon the numerous consequences
of the above established principle. I shall only
observe, that when death commences by the circulatory
system, the preceding phenomena are not to be remarked,
or at least very little perceptible.
Let us now pass on to the influence of the black blood
upon the organs of which it penetrates the tissue.
To determine what the influence of the black blood is
upon the organs, I shall first remark, that the property of
the red blood is to stimulate them, and keep up their vital
actions. This will be proved by the following observations:
1st, Compare phlegmon, erysipelas, and inflammatory
tumours (to the formation of which the red blood is
essentially requisite) with scorbutic spots, and petechiæ,
produced by the black blood. The first will be found
connected with the exaltation of the vital powers, the
second with their depression.
2dly, Examine two men, the one with a rosy coloured
skin and large breast, announcing vigour of lungs, the
other with a pale and sallow countenance, and narrow
chest: in these the vigour of the chemical combinations
which are made in the lungs, should certainly be very
different.
3dly, The greater number of gangrenes in old men,
begin with a lividity in the part, a lividity which is
evidently the index of the absence or diminution of the
arterial blood in the part.
4thly, The redness of the branchiæ of fish is always
the sign by which their vigour may be recognised.
5thly, The redder the granulations of wounds, the
more healthy is their nature; the paler or browner they
are, the less has the part a tendency to cicatrise.
6thly, The lively colour of the face, and the ardent
eye, coincide with the energy of the cerebral actions in
certain fevers.
7thly, The more developed the pulmonary system of
animals, the more active are the chemical processes of the
lungs, and the more developed and perfect the general
life of their different organs.
8thly, Youth, which is the age of vigour, is that also
when the red blood predominates in the system. The
arteries of old people are smaller, the veins larger than
those of the young. It is a fact universally known, that
at the two extremities of life the proportions of the two
vascular systems are inverted.
I am ignorant of the manner in which the red blood
excites and keeps up the life of the parts. Perhaps the
principles by which it is coloured become combined with
the different organs to which it is distributed. In fact
there is a considerable difference between the phenomena
of the general and those of the capillary system.
In the first, the blood in changing its colour, leaves
behind it the principles which made it red; in the second,
the elements to which its blackness is owing, are rejected
by respiration and exhalation. Now, this union of the
colouring principles of the arterial blood, may probably
constitute a material part of the excitement which is
necessary to the action of the organs.—If such be the
case, the black blood as it does not contain the materials
of such union, cannot act as an exciting cause. This idea,
however, I offer only as a probability, and am by no
means prepared to defend it as a truth; it may be ranked
on a par with that of the sedative action, which I have
said may be excited by the black blood on the different
parts—for, however probable an opinion may appear,
there should be no real importance attached to it as an
opinion only.
Without regard then to any system, let us inquire
how the black blood, from its contact with the various
parts, is the occasion of their death; how it acts on the
parts of the animal life, and how it acts on those of the
organic life.
All the organs of the animal life depend upon the
brain; now, we have seen that the black blood paralyses
the cerebral powers almost suddenly. In the state then
of asphyxia, the locomotive, the vocal and sensitive
organs, must be inactive. From the same cause, their
exercise must be suspended in all those different experiments
where black blood is injected into the brain, the
other parts receiving the red blood as usual. But when
the black blood circulates throughout all the system,
when the whole of the organs, as well as the brain, are
submitted to its influence, then there are two other causes
of death connected with those which have been mentioned.
1st, The nerves, which are penetrated by it, for that
very reason are no longer capable of keeping up the communication
between the brain and the senses on the one
hand, and on the other, between this same viscus and the
locomotive or vocal organs.
2dly, The contact of the black blood with these organs
themselves annihilates their actions. Inject the crural
artery of an animal with the black blood taken from one
of its veins, and the movements of that member will be
shortly afterwards enfeebled, or wholly paralyzed. In
this experiment, the upper part of the artery, for manifest
reasons, should be that to which the pipe of the syringe
should be fixed.
I am aware that as to this experiment, it may be asserted
that the ligature of the artery, of itself, is capable
of paralyzing the limb. In fact, such circumstance has
happened twice with me, but I have also had occasion to
observe, that it does not necessarily follow the ligature
of this vessel, as it does the ligature of the aorta: when
the latter vessel is tied, all movements cease at once;
notwithstanding all which, the result of the injection of
black blood, is almost constantly that which I have asserted
it to be;—I say almost, 1st, Because I have once seen
it fail in its effect, though done with the requisite precautions;
2dly, Because the debility, which is induced, both
in duration and degree, will be according to the strength
of the animal on which the experiment is made.
There is also occasioned in this experiment, a manifest
suspension of the sensibility of the animal; it is not
indeed so ready to appear as the loss of motion; but it
always comes on, especially if the injection of the black
blood be repeated three or four times, with small intervals.
A similar, but a more tardy effect may be produced
by adapting to the canula, which has been placed in the
crural artery of an animal, a tube which has been previously
fixed to the carotid of another animal, and then
by asphyxiating the latter.[96] The organs of the internal
life are not dependent on the brain, and therefore are
not affected by the suspension of the cerebral action in
asphyxia. It is the influx of the black blood which is the
immediate cause of their death.
I have already demonstrated what the influence is of
this blood upon the organs of the circulation. We have
seen how the heart ceases to act, as soon as it is penetrated
by it; it is owing in part to the injection of the arterial
and venous parietes themselves, by the vasa vasorum, that
the vessels are forced to suspend their actions.
It will be always a difficult thing to prove, that the
secretions, the exhalations, and the process of nutrition,
could not be made from venous blood, because the circulation
of this sort of blood in the arteries, does not continue
for a sufficient time, to allow of observations, or the
manner in which these functions would be affected by it.
On this subject, however, I have made some essays. 1st,
I exposed the inner surface of the bladder of a living
animal, after having previously divided the symphysis
pubis, and opened the lower belly, I then examined the
oozing of the urine from the orifices of the ureters,
while I asphyxiated the animal. 2dly, I divided the vas
deferens, with the view of observing, whether the semen
would flow or not, during such state.
In general, I have had occasion to remark, that during
the circulation of the black blood in the arteries, no fluids
appear to issue from the different secreting tubes. But I
confess, that in all these experiments, and in other similar
ones which I have made, the animal is too much agitated,
and the limits of the experiments too circumscribed, for
any thing like a well founded judgment to be formed
on the subject in question. It is chiefly from analogy,
then, that I am led to conclude, that the black blood is
unfit for the purposes of exhalation and nutrition: such
supposition also accords well with divers of the phenomena
of asphyxia.—1st, The want of exhalation from
the skin during the state of asphyxia, is probably the
reason of the phenomena of the animal heat in such sort
of death.[97] 2dly, In asphyxiating animals very slowly
during digestion, I have uniformly observed, that the bile
ducts, and duodenum, contain a much less quantity of bile,
than they do at such time, when these parts are exposed
in the living animal.—3dly, As the blood loses nothing
from the exercise of these functions, it must of course
accumulate in the vessels; and in fact, it is very fatiguing
and unsatisfactory, to dissect the bodies of those who
have been hanged or asphyxiated with the vapours of
charcoal, from the fluidity and abundance of their blood.
But this abundance, perhaps, may depend upon the
weakness of the absorbents. In other sorts of death, the
absorbents continue for some time to act upon the serous
portion of the blood remaining in the vessels. In asphyxia
there is neither secretion nor absorption.
The excretions also appear to be affected much in the
same way. The bladder of asphyxiated persons has been
observed by Portal, to be very much distended. Such
distension, no doubt is occasioned by the urine already
secreted before the accident which was the cause of their
deaths. In general, the asphyxiæ which are occasioned
by the circulation of the black blood unmixed with any
deleterious substance, are not accompanied with those
spasms, which in so many other sorts of death, are so
frequent. These spasms, which evacuate the organs of
their fluids, should be carefully distinguished from the
simple relaxations of the sphincters, by which analogous
effects are produced.[98] In asphyxia, all is debility, in
asphyxia, we never see that augmentation of life, that
development of power, which so frequently mark the
latter movements of the dying.
Hence also perhaps, the great flexibility of the members
of asphyxiated persons. The stiffness of the muscles
appears to depend in many cases, on the circumstance of
death having come on precisely at the moment of their
contractions. The fibres remain approximated, and coherent
among themselves;[99] in asphyxia, on the contrary, as
there exists an universal relaxation and want of action in
the parts, they remain so after death, and yield to whatever
impulse may be communicated to them.
I confess, however, that this explanation is subject to a
difficulty which I cannot solve. Persons asphyxiated by
mephetic vapours, perish nearly in the same way as those
who are drowned; if the cause of their death be different,
its effects are the same, as may be seen by opening the
carotid of two dogs at the same time, that into the lungs
of the one are injected the vapours of charcoal, and into
those of the other, a certain quantity of water, which
water, as in the drowned, is soon reduced into a state of
foam.
Notwithstanding this similitude of the last phenomena
of life in the two cases, the members in the first remain
for a certain time warm and supple, while those in the
second, especially if the body be plunged into water
during the experiment, become very suddenly stiff and
frozen. Let us return, however, to our subject. We
may conclude from the various facts and considerations
related in this chapter, 1st, That when the chemical
functions of the lungs are suspended, the functions of all
the other organs are suspended also, from the presence
of black blood within their substance. 2dly, That the
death of the organs in general, coincides with that of
the brain, and the heart, but is not immediately derived
from them. 3dly, That if it were possible for the brain
and heart to receive an influx of arterial blood, while
the others were dying, from that of the venous blood,
they would doubtless continue to exert their accustomed
actions. 4thly, That, in a word, asphyxia is a general
phenomenon, developed at the same time in all the organs,
but especially in one of them.
From this manner of regarding the influence of the
black blood upon the different parts of the body, it appears
that death is very soon the result of its circulation in the
arteries. Nevertheless, certain organic defects have
sometimes prolonged after birth, the mixture of the two
sorts of blood, a mixture which is known to be made in
the fœtus. Such was the malconformation mentioned
by Sandeford, in a child, the aorta of which arose by a
branch from each of the ventricles. Such also appears,
at first sight, to be the opening of the foramen ovale in
the adult.
We shall remark, however, that the existence of this
foramen, does not suppose the passage of the black blood
into the red-blooded auricle, as is generally believed.
For the two semi-lunar valves, between which it is situated
when met with after birth, are necessarily applied to
each other by the pressure which the blood contained in
the auricles, exercises upon them, when these cavities are
simultaneously contracted. The foramen must be at such
time shut, and its obliteration much more exact, than that
of the opening of the ventricles, by the mitral and tricuspid
valves, or that of the aorta and the pulmonary artery,
by the sigmoid valves. With all this, the foramen ovale
is actually very often found open in the subject, and when
not so, nothing is easier than to destroy the species of
adhesion which is contracted by the two valves which
close it. This may be done with the handle of a scalpel,
without any solution of continuity, the parts appear to be
unglued.
The oval hole when in this way artificially made, presents
the same disposition, with that which is sometimes
exemplified in the carcase. Now if this disposition be
examined, it will be seen that when the auricles contract,
the blood must make an obstacle to itself, and that it
cannot pass from one into the other of these cavities. It is
an easy thing to be convinced of the mechanism of which
I speak, by means of two injections of a different colour,
made at the same time from both sides of the heart, from
the vena cava, and the pulmonary veins.
From what we have said of the influence, which is
exercised by the movement and the different principles
of the blood, it is evident that the death of the white
organs must be different from that of the red ones.
Asphyxia can hardly reach them, but of the manner in
which they die I confess that I know but little.
In recapitulating what has been said in the preceding
chapters, with respect to the influence of the lungs over
the heart, the brain, and all the organs, it is an easy
matter to form an idea of the successive termination of
the whole of the functions, when the phenomena of respiration
are suspended either mechanically or chemically.
The following is the manner in which death supervenes,
when the mechanical phenomena of the lungs are interrupted,
either from the causes mentioned in the 5th
chapter, or from similar ones, such as the rupture of the
diaphragm, which I have twice had occasion to observe,[100]
or from a fracture of a great number of the ribs, or the
sternum.
1st. The mechanical functions of the lungs cease. 2dly.
The chemical functions of the lungs cease also. 3dly.
The cerebral actions are put an end to. 4thly. The animal
life is interrupted. 5thly. The general circulation
is interrupted. 6thly. The capillary circulation is interrupted.
The phenomena of death, are differently concatenated,
when they begin by the suspension of the chemical
functions of the lungs: which may happen, 1st, From
breathing in a vacuum; 2dly, From the obliteration of
the passage of the trachea, by foreign substances introduced
into it, or by tumour from without, or strangulation,
accumulation of fluid in the air cells, &c.; 3dly, From
different inflammatory affections, schirrhi, &c. of the
cavities of the mouth or throat. 5thly, From want of
respirable air, as on the summit of high mountains. 6thly, From
the introduction into the air cells of non-respirable
gases, &c. &c. In all these cases, the following is the
order of the phenomena of death.
1st. The chemical functions of the lungs are suspended.
2dly. The functions of the brain are interrupted. 3dly.
Sensation, locomotion, the voice, the mechanical phenomena
of respiration cease. 4thly. The action of the
heart, together with the general circulation is annihilated.
5thly. The capillary circulation is put an end to, together
with the processes of secretion, exhalation, absorption,
and digestion. 6thly. The animal heat of the system
dies away.
The influence of the black blood as I have said, is
always the great agent in this double sort of death, but
it is not the only one: if that were the case, the phenomena
of all the asphyxiæ would be alike. It is true
that in every sort of asphyxia, the black blood ceases to
become red blood, and circulates in the arteries, such as
it is in the veins; but notwithstanding the uniformity of
this phenomenon, there can be nothing more varied, than
the symptoms and progress of these accidents. In some
of them, death is long in taking place; in others, almost
instantaneous: the phenomena developed in the last
moments of existence, are alike in none of them. The
state of the organs, and that of the powers which they
preserve after death, are as various.
1st, Asphyxia varies with respect to its duration; in
sulphurated hydrogenous gas, in nitrous gas, and certain
vapours arising from privies and sewers, it is quick in
taking place. In carbonic acid gas, azote, in pure hydrogen,
water, and a vacuum, its progress is slower.
2dly, Asphyxia varies with respect to its attendant
phenomena. At times, the animal is violently agitated
and suddenly convulsed; at others, it appears to lose its
powers gradually; to pass into a state of sleep, and from
sleep into a state of death. In comparing the numerous
effects arising from the vapours of sewers, from those of
charcoal, from the different gases, from drowning, and
other causes of asphyxia, we find them almost as various,
as the causes themselves.
3dly, The phenomena which make their appearance
after death, are as variable. Compare the cold and frozen
carcase of a drowned man, with the remains of one who
has been suffocated. Read the result of the different
experiments of the Institute, upon the affections of the
galvanic fluid in the different asphyxiæ; examine Halle’s
detail of the symptoms which accompany the mephitism
of sewers; approximate the numerous observations, which
are scattered about in the works of Portal, Louis, Haller,
Troja, Pechlin, Bartholin, and Morgagni; repeat the most
common experiments on the submersion, strangulation,
and suffocation of animals; and you will observe the
greatest difference in all these sorts of asphyxia, they are
each of them characterized, by a peculiar state of the
bodies of the animals, which have been submitted to
the experiment.
To inquire into the causes of such differences, we must
first divide the asphyxiæ into two classes. 1st, Into those
which happen from the simple want of respirable air, and
2dly, Into those, where to this first cause is joined also
that of the introduction of some deleterious substance
into the lungs.
In the first class, the immediate cause of death, appears
to be the simple presence of the black blood, in the various
parts of the body, the general effect of which is always
the same, in whatever manner produced; accordingly, the
attendant symptoms and secondary results of all these
sorts of death, are nearly alike, their duration the same,
and if it varies, it varies only in consequence of the more
or less complete interruption of the passage of air into the
lungs.
This variety in the duration and intensity of the
asphyxiating cause, may nevertheless occasion some variety
in the symptoms also; such as a greater or less lividity
and swelling of the face, a more or less considerable
embarrassment of the lungs; but all these differences
indicate only so many modifications of the cause, 1st, A
man who is hanged, does not die as a man who is suffocated
by an inflammatory tumour, or a pea or bean which
perchance may have fallen into the trachea.[102] 2dly, An
animal will perish much more slowly under a vessel of
air, than when the trachea is tied. 3dly, The symptoms
of asphyxia, when occasioned by a great rarefaction of air,
or by a suffocating heat, are much less slowly produced,
than where the cavity of the lungs is opened.
In all these cases the cause of death, namely the absence
of red blood in the arterial system, is simple and unique,
but according to the greater or less oxygenation of the
venous blood, will be the appearances after death, for the
longer the process of asphyxia endures, the less irritability
will there be found in the system.
But if the cause of asphyxia, have been the introduction
of some deleterious fluid into the lungs, then the
variety of the symptoms will depend upon the difference
in the nature of the fluid. In these cases the cause is
of two kinds: 1st, There is no red blood in the system.
2dly, A pernicious fluid is present in the system. All
the gases however do not act as deleterious substances:
in pure hydrogen for instance, the animal perishes only
as it would from the want of respirable air.
But when a man in descending into a common sewer,
into a cellar, or into any place where putrid matters are
accumulated, falls into asphyxia at the moment when he
inspires their exhalations, and when such state is attended
with convulsive movements and extreme agitation, then
indeed, there must be something more in the cause of his
death, than a simple suspension of the chemical functions
of the lungs.
In fact, together with the mephitic vapour, there continues
to enter into the lungs a sufficient quantity of air
to keep up life and its different functions. 2dly, Supposing
even that the quantity of mephitic air were such as
to leave no place for the entrance of respirable air, still
the death ensuing should only be gradual, without agitation
and convulsion, were it occasioned only by the
absence of such air: now the very different way in which
it supervenes, very evidently indicates the action of a
deleterious substance, upon the animal œconomy.[103]
These two causes then act together, in those asphyxiæ
which are produced by certain gases, sometimes the one
predominates, sometimes the other. If the deleterious
substance be violent, it kills before the action of the black
blood can have produced much effect, if weak, it is the
black blood, which is principally the cause of death.
The asphyxiæ then, which are produced by the gases,
differ only, in consequence of the nature of the deleterious
substance, which varies ad infinitum. In some of the
aeriform fluids indeed it is supposed to be known, but in
the greater number of them it is not so:[104] I shall notice
therefore in a general way the effects, which result from
the action of the deleterious substance, remarking at the
same time, that the symptoms by which they are displayed,
are strongly or weakly marked, according to the age
and temperament of the individual.
Deleterious substances introduced into the lungs, together
with the mephitic vapours of which they form
a part, can act only in two ways. 1st, By affecting the
nerves of the lungs, which re-act on the brain. 2dly, By
passing into the blood, and exercising their influence, by
means of the circulation on the various organs of the
system.
I can easily believe that the simple action of such a
substance on the nerves of the lungs, may have a very
marked effect on the economy, and be capable of troubling
the functions of the system very sensibly; much indeed
in the same way as with some individuals a mere odour,
or the sight of a hideous object, will occasion syncope, in
the same way that an irritating enema will suddenly
awake the system into life, or the introduction of certain
substances within the stomach, will be felt throughout
the body, before such substances can have passed into the
circulatory torrent. We meet at every moment with
examples of these very remarkable phenomena, produced
by the simple impressions of foreign bodies on the mucous
surfaces; I cannot deny that deleterious substances may
act in the same way upon the nerves of the lungs, though
we must not exaggerate the sphere of this mode of action.[105]
In fact, I am not acquainted with any one example,
where the contact of a deleterious substance with a
mucous membrane, has been the sudden cause of death.
It may indeed be productive of such effect after a certain
time, but never at the moment of its action; nevertheless,
in those asphyxiæ which are produced by mephitic
vapour, so rapidly does death come on, that the black
blood can scarcely have had the time to exert its influence
upon the body. The principal cause of the cessation of
the functions is manifestly the action of the pernicious
substance.
These considerations, then, incline me to believe, that
these substances pass into the blood through the lungs,
and that in circulating with the blood they carry to the
organs the immediate cause of their death. Such passage
into the blood has already been suspected by many physicians;
the truth of the fact appears to be indubitably
proved by the following reflections.
1st, It can hardly be doubted, that the poison of the
viper and many other venomous animals, and that the
saliva of rabid animals, pass into the system of the blood,
and are taken up either by the veins or the lymphatics.
2dly, It appears to be very certain, that a portion of the
atmospheric air is actually absorbed through the mucous
membrane of the lungs itself, and not by means of the
absorbent system. Now, if this be the case, I know not
what should hinder the passage of mephitic vapour in
the same way.[106] We are not sufficiently acquainted with
the limits of the particular sensibility of the membrane
of the air cells, to say that it cannot give a passage to
such vapour.
3dly, The respiration of an air which has been charged
with the exhalations arising from oil of turpentine, communicate
a particular smell to the urine. It is thus that
this fluid is affected from the residence of the persons in
a newly varnished room. In this case it is evidently
by the lungs in part, that the odoriferous fluid has its
passage into the blood, and so on to the kidneys. In fact,
I have often assured myself by breathing out of a bottle
through a tube, air so charged (in which case it could not
act on the cutaneous surface) that the smell of the urine
undergoes a change. If, then, the lungs will admit a
variety of substances, which do not enter into the composition
of respirable air, for what reason should they not
admit the mephitic vapour of mines and subterraneous
places.
4thly, The respiration of humid air produces dropsy.
The extent of the fact has been exaggerated, indeed, but
the fact itself is true. It proves, that an aqueous fluid
may pass into the blood, and consequently that other
substances may pass into it also.
5thly, If an animal be asphyxiated in sulphurated hydrogenous
gas, and a plate of metal some time after its death
be placed under one of its muscles, the surface of the plate
contiguous to the muscle, will be sensibly sulphurated.
The foreign principle, then, which is here united with
the hydrogen, must have been introduced into the circulatory
torrent by the lungs, and have penetrated with the
blood into all the parts. The deputies of the Institute
have observed this phenomenon in their experiments. I
have made a similar remark in asphyxiating animals with
nitrous gas. A phenomenon of the same nature accompanies
the exhibition of mercury.
From the above, we have nearly a right to conclude,
that the different deleterious substances of which the gases
are the vehicles, do actually pass into the blood, and so
affect the organs. Of this matter, however, I shall
adduce some further proofs.
I have ascertained by a number of experiments, that
atmospheric air, or any other aeriform fluid, may be made
to pass into the blood without alteration.
Divide the trachea of a dog, inject the air-cells strongly
with common air, and continue to retain it in the lungs.
The animal will immediately discover signs of great
distress and agitation; if an artery now be opened, the
blood will be emitted in a frothy state.
If hydrogen have been employed, it may easily be
ascertained that the nature of the fluid is unchanged, by
placing a candle over the bubbles which are disengaged.
When the blood for the space of thirty seconds has
flowed in this state, the animal life of the creature will
be finished, and death ensue, with all the symptoms which
accompany the insufflation of air into the black-blooded
system of vessels. The re-admission of air into the
lungs, will have no effect in restoring the animal to life,
for as soon as frothy blood can flow from any one of the
arteries, it must already have affected the brain with its
pernicious influence.
In this case it may be perceived, that the causes of death
are the same as those which proceed from the insufflation
of air into a vein. In the one instance the air passes
at once from the lungs into the arterial system. In the
other, from the veins across the lungs and then into the
arteries.
When we open the bodies of animals, which have been
killed in these experiments, the whole apparatus of the
red-blooded vascular system, is found to be filled with air
bubbles of various sizes. In some circumstances, the
blood will be transmitted in the same state into the general
capillary system, and from thence into the veins; in
others it will be stopped in the capillary system, and
in such cases, though the circulation may have continued
for some time after the suspension of the animal life, not
a single particle of air will be discovered in the veins.
In these experiments which I have frequently repeated,
I have never found that the least fissure has been made in
the bronchiæ; nevertheless, I confess that it is difficult to
say, whether this be so in their last ramifications. The
following phenomenon, however, may throw some light
upon the subject; for as often as air is pushed into the
lungs with great violence, there will be produced an
emphysema of the breast, or neck, from the infiltration
of this fluid among the cellular texture, in addition to its
passage into the blood. But if the impulse be moderate,
and the quantity of air injected not much beyond the
measure of a full inspiration, it will pass into the blood
only, and not into the cellular texture.[107]
The experiments of which I have given the detail, exemplify
phenomena which do not indeed take place in the
ordinary process of inspiration, and therefore I allow that
no very rigorous induction can be drawn from them, with
respect to the passage of deleterious substances into the
mass of the blood; nevertheless it appears to me, that
they very much confirm the probability of such fact,
which besides is demonstrated by many of the preceding
remarks. I shall conclude, then, that such passage is real.
In fact, we have seen 1st, That the sole transmission of
the black blood into the arteries, will not account for the
infinitely various phenomena exemplified in the different
sorts of asphyxiæ; 2dly, That the simple contact of the
deleterious substance with the nerves of the lungs, can by
no means be the cause of a death so rapid as that which
is occasioned by these accidents; 3dly, That, therefore,
we are forced as it were to suspect the passage of the
poison itself into the blood; 4thly, That a number of
considerations are in favour of such suspicion, and thus
that the fact is proved both directly and indirectly.[109]
This principle being once established, a variety of
results must flow from it. Of the first of these, of the
mode of action, namely, which the deleterious substance
must exercise upon the different organs, I shall say
nothing, having nothing to offer but conjecture.
I shall accordingly content myself with inquiring what
system it is which is particularly influenced by these
substances, when mingled with the blood.—Now, 1st,
This system appears to be the nervous one, and that
portion of it especially, which presides over the parts of
the animal life, the organic functions being only secondarily
affected; 2dly, Of all the nervous system, the brain
is that part which is the most affected; 3dly, Under this
relation Monsieur Pinel appears to me to have been right,
in placing some of the asphyxiæ (those for instance which
are occasioned by the presence of a deleterious substance)
among the neuroses. On this head the following considerations
should leave us little doubt.
1st, In all the asphyxiæ, when the presence of a deleterious
substance cannot be doubted, the symptoms consist
of two general and opposite sets of phenomena, of spasm
and torpor. Of two workmen who had come up out of
the sewer of the street St. André des Ares, the one
sat himself down upon a bulk, and fell into a state of
asphyxia; the other with irregular convulsive movements,
proceeded as far as the rue Battoir, and then fell down
asphyxiated. The Sieur Verville, in consequence of
inhaling the breath of a man who was lying in a state
of asphyxia from the vapour of lead, fell down suddenly,
and in a short time became convulsed. The vapour of
charcoal intoxicates, as it is said. I have seen animals
asphyxiated with other gases, and perishing with a stiffness,
such as could be produced only by the most violent
spasm. The centre of all these symptoms, and the organ
from which they emanate, undoubtedly is the brain, and
they depend upon its irritation or compression.
2dly, The animal life is always interrupted before the
organic life, wherever the asphyxiating cause has been of
a compound nature. Now the centre of the animal life
is the brain.
3dly, I have proved when the animal perishes from
the circulation of the black blood in the arteries, that the
brain is especially affected even then; but in the same
way, that is, by the cephalic arteries, the deleterious substance
itself, may be introduced into the brain.
4thly, I have pushed a variety of deleterious gases (for
example, sulphurated hydrogen) into the brain, and also
some of those substances which vitiate the nature of these
gases. The animal has always perished with symptoms
of spasm, or torpor, and in general the death which is
occasioned by the different gases, is always similar to that
which is produced by the introduction of pernicious substances
into the brain.
5thly, The consequences of these asphyxiæ, when life
has been restored, invariably suppose a lesion of the
cerebral system, such consequences consist of palsy, tremour,
wandering pains, and derangements of the exterior
apparatus of the senses.
From all these multiform experiments and considerations,
we may surely conclude, that it is on the brain and
nervous system that the deleterious principle, introduced
into the blood, must act; from the death of these parts,
that of the others is derived.
In this case the different organs no doubt are directly
enfeebled, and may perhaps be immediately affected by
those principles, which flow into them together with the
blood, but all such phenomena, are even more visible in
the animal, than in the organic life.
Let us not forget however, that a part at least of the
cause of this sort of death, consists in the influence of the
venous blood upon the organs, and that this influence
must ever be in proportion to the length of time that
such blood continues to circulate. The differences then
which are found in the asphyxiæ, may be said to proceed
from the greater or less effect of the venous blood upon
the system, from the different nature of the various
deleterious substances inspired, and from the age and
temperament of the individual affected.
I have just spoken of sudden death. I shall now
enlarge a little on that which is the slow effect of disease.
Physicians must be well persuaded, that by far the greater
number of diseases, put an end to life by an affection of
the lungs. Whatever be the seat of the principal affection,
be it either an organic lesion, or a general disorder
of the system, the action of the lungs in the latter
moments of existence, becomes embarrassed, the respiration
difficult, and the oxydation of the blood, but slowly
effected; accordingly this fluid must pass into the arteries,
almost in the venous state.
The organs therefore which are already enfeebled, must
be much more readily affected by the pernicious influence
of such blood, than those which are subject to it, in the
different cases of asphyxia. In this way the loss of
sensation, and intellect, are very shortly the effect of
embarrassment in the lungs; and ensue as soon as the
brain begins to be penetrated with the fluid which is so
transmitted to it.
By degrees the heart and all the organs of the internal
life, cease also to move. It is here the black blood
which arrests these vital motions, which have already
been enfeebled by the disease. Such weakness, the consequences
of the disease, is very rarely the immediate
cause of death, it only prepares it, by rendering the
organs more susceptible of the alteration in the healthy
state of the blood. Such alteration is almost always the
immediate cause of death. The disease then, is only an
indirect cause of death in general, it kills the lungs, and
the death of the lungs occasions that of all the other
parts.
From hence it may be easily conceived, why the small
quantity of blood contained in the arterial system of the
subject, is almost always black. For 1st, The greater
number of deaths begin by the lungs. 2dly, We shall
see that those which have their commencement in the
brain, are equally the cause of this phenomenon. Accordingly
there can be only those, in which the heart ceases
suddenly to act, after which the red blood can be found
in the aortic ventricle, and auricle. Such appearance is
seldom found, excepting in the bodies of persons who
have perished from extensive hemorrhagy.
From the frequency of deaths beginning with an embarrassment
of the lungs, may be conceived also the reason,
why this organ is so frequently gorged with blood in the
carcase in general, the longer the agony, the heavier
and fuller are the lungs. When such fulness is found,
together with black blood in the red-blooded system,
whatever the disease may have been, it may be pronounced
that death has begun in the lungs. In fact the concatenation
of the phenomena of death is from one of the
three organs, from the lungs, brain, or heart, to all the
others. Now when death begins in the heart, the pulmonary
vessels are generally empty, and there is red blood
in the aortic system. On the other hand, if death has
begun in the brain, there is then indeed a certain quantity
of blood in the arteries, but the lungs are empty, unless,
when gorged with blood, by some antecedent affection.
As soon as the human brain ceases to act, the functions
of the lungs are suddenly interrupted; this phenomenon,
which is constantly observed in the red and warm-blooded
animals, can happen only in two ways. 1st, Because
the action of the brain, is directly necessary to that of
the lungs, or 2dly, Because the latter receives from the
former, an indirect influence by means of the intercostal
muscles and diaphragm, an influence, which ceases with
the activity of the cerebral mass. Let us try to determine
which of these two modes is that of nature.
I shall have proved that the death of the brain, is not
immediately the occasion of that of the lungs, if I can
determine that there is no immediate influence exercised
by the first, upon the second of these organs, now, this
essential principle may be easily demonstrated by experiment.
The brain can exercise an immediate influence on the
lungs, only by means of the par vagum or the great
sympathetic nerve, the only nerves, which according to
the common opinion, establish a communication between
the two organs (an opinion however which is erroneous,
as the great sympathetic is only an agent of communication
between the organs and the ganglions of the system.)
Now 1st, The influence which is derived by the lungs
from the par vagum, is not actually necessary for them
to act. The following experiments will show the truth
of this assertion.
1st, Irritate the par vagum on one or both sides, and
the respiration of the animal will be somewhat quickened;
but such appearance is no proof of an immediate influence,
for any wound of the neck, or any wound whatever,
provided that it be the occasion of considerable pain, will
be the cause of a similar phenomenon.
2dly, Cut one of the nerves, and the respiration will
be at once affected, as when the nerve is irritated; but
as soon as the pain ceases, the embarrassment of the lungs
will disappear; and at the end of four and twenty hours,
the phenomena of life be concatenated with their accustomed
regularity.
3dly, Divide these nerves on both sides. In this case
the breathing will be much more precipitated, and will
not return to its ordinary state, as in the preceding experiment;
it continues laborious for four or five days, and
the animal perishes.[110]
From the two latter experiments it follows, that the
par vagum is indeed necessary to the phenomena of
respiration, and that the brain must exercise, of course,
an influence over this function, but at the same time, it
may be seen, that without the immediate influence of the
brain, the lungs will continue in play, and consequently
that the interruption of such influence, as when the brain
is injured, will not be an immediate obstacle to the continuation
of the pulmonary actions.
The question whether the functions of the lungs are
more immediately connected with the influence derived
from the ganglions, may be decided by the following
facts.
1st, If on the one and the other side of the neck, the
nervous thread be cut, which is usually regarded as the
trunk of the great sympathetic, there follows little or no
alteration in the phenomena of respiration.
2dly, If the par vagum and the great sympathetic be
divided at the same time on both sides of the neck, the
animal will die after a certain time, and much in the same
way, as when only the par vagum is divided.
3dly, When we divide the sympathetic nerve in the
neck, we do not deprive the lungs of the nerves which
come from the first thoracic ganglion; now these nerves
may contribute to keep up the action of the lungs, since,
as I have said, each ganglion is a nervous centre, capable
of emitting its own peculiar irradiations, independently of
the other centres, with which it communicates.
But whether the nerves, which are derived from the
first thoracic ganglion, do really assist the functions of
the lungs, I have not been able to ascertain by experiments
on the nerves themselves, for such is the position
of the first thoracic ganglion in most animals, that it
cannot be taken away without doing so much injury to
the parts as would kill the creature, or throw it into such
agitation, as wholly to confound the phenomena of which
we are in search, with those of a general distress and
trouble. From analogy, however, and from the destruction
of other ganglions, by which the internal organs are
supplied, we should not have a right to suppose that the
lungs would cease to act, when the ganglion in question
is destroyed.
Besides, the following reasons appear to me to prove
unquestionably, the principle which I advance. If great
lesions of the brain have the effect of suddenly interrupting
respiration, because this organ can no longer influence
the lungs by means of the nerves, which come from the
first thoracic ganglion, it is evident that if all communication
between the brain and this ganglion be taken away,
such influence must cease, and respiration be suspended;
but if we divide, as Cruikshanks has done, the spinal marrow
on a level with the last of the cervical vertebræ, the
animal will continue to live and breathe for a length of
time, notwithstanding the want of communication between
the brain and the lungs, by means of the first thoracic
ganglion. From the above experiments, we may conclude,
that the brain does not exercise any direct and
actual influence over the lungs, and consequently that
other causes must be sought for, if we mean to account
for that sudden and instantaneous cessation of the functions
of the latter of these organs, when those of the
former are suspended.
There exists, notwithstanding, a phenomenon which
seems to cast some doubt upon the conclusion which I
have deduced, and in the principle which it establishes.
I speak of the sudden difficulty of respiration, and that
impeded circulation which are occasioned by violent pain.
This distress appears to indicate that the heart and the
lungs are dependent immediately upon the brain; for the
distress is in the brain, say the greater number of authors,
and the affection of the heart and lungs, a consequence of
the reaction of the brain; but here let it be remembered,
that almost all pain is made up, first of sensation, and
secondly of some emotion, passion or affection.[111] Now
as I have proved at length, in the former part of this
work, all passion and emotion have their seat in the internal
viscera, and thus it will appear, that the trouble which
in such case is felt in the heart and lungs, does not depend
upon the brain for its cause, but is the immediate effect
of the passion, or emotion, which accompanies the sensation.
The following considerations will bear me out in
this conclusion.
1st, In many instances the dyspnœa and impeded circulation,
precede the pain. Examine the thorax, and place
your hand upon the heart of a man about to undergo an
operation, and you will be easily convinced of this truth.
2dly, There is sometimes a manifest disproportion between
the sensation of pain, and the distress which is
experienced about the heart, and in breathing. I have
known the operation of cutting away the prepuce immediately
fatal. Now in this case, it surely could not be
pain which killed the man.
3dly, There are many persons who are capable of supporting
violent pain, with resolution. Place your hand
upon the heart of such persons, and no agitation whatever
will be felt there. Nevertheless, their perception of pain
must be what it is in other persons.
4thly, In the course of an operation, we are not to
judge of the patient’s state of mind, from his cries, or
silence. This sign is very deceitful; because a man may
be sufficiently master of himself to overpower the influence
of his internal organs. We must examine the heart
and lungs; their functions, if I may allow myself the
expression, are the thermometer of the affections of the
mind. It is not without reason, that the actor who plays
the part of a courageous man, takes hold upon the hand
of him whom he wishes to set at ease, and lays it on his
heart. The exterior movements of the passions, are not a
fair criterion of the inward feelings of the individual, for
these movements may be feigned as well as real: feigned
if they originate in the brain: real if they have their
sources in the heart;—in the first case voluntary, in the
second involuntary. Touch the pulse of the angry man,
if you wish to know whether he really is in anger.
When I see a woman weeping or convulsed at any distressing
news, and find her pulse in its natural state, I
know what to judge of her affliction.—On the contrary,
if her grief be concentrated, but her heart beat strongly,
or her pulse have been suddenly depressed, I know that
she feigns a calm which she does not feel. To judge
correctly, we must always compare the external movement
with the state of the internal organs. There could
be no deceit, were it possible to distinguish the involuntary
movements produced in a state of passion, by the
action of the heart upon the brain, and then by the reaction
of the brain upon the muscles, from the voluntary
movements which are occasioned by the simple action of
the brain upon the locomotive system.
However strong may be the pain which has been the
occasion of the dyspnœa, and impeded circulation, of
which we have been speaking, this dyspnœa and distress
about the precordia, will cease, provided only that the
pain be continued. Nevertheless, if the reaction of the
brain were the real cause of the distress in question,
the contrary should be the case; for the continuation of
the affection of the brain, should continue also to cause
its re-action. But here the effect of habit is evident,
though the pain subsists; the brain indeed continues to
be affected, but the internal organs cease to be so. It
may be easily perceived, that I am not here speaking of
those cases, where the action of the heart and lungs has
been deeply troubled by the effect of pain.
To the above considerations I might add many others,
with the view of proving, 1st, That although the brain
be the seat of the pain, it is not the source of those affections
of the internal organs, which are occasioned by
such pain; 2dly, That these affections depend upon an
emotion, which is absolutely distinct from sensation of
whatever kind, both in its nature and effects.
Since the death of the lungs, upon the cessation of the
cerebral action, is not direct, there must exist between
the brain and the lungs, some intermediate agents, the
cessation of whose functions, occasion the cessation of
those of the lungs. These agents are the diaphragm, and
intercostal muscles; for they depend immediately upon
the brain by means of the nerves, which they receive from
it, and consequently become paralytic on the death of the
brain; the following experiments are a proof of the fact.[112]
1st, Cruikshanks divided the spinal marrow of a dog
between the last cervical, and the first dorsal vertebræ.
The intercostal muscles accordingly were immediately
paralyzed, and the breathing of the animal continued to
be made by the diaphragm only, which receives the
phrenic nerve from a point above the section. In this
experiment, it is easy to judge of the strong action of the
diaphragm, by that of the abdominal muscles.
2dly, If the phrenic nerves only be divided, the diaphragm
becomes immoveable, and then the respiration of
the animal is effected by the intercostal muscles only.
3dly, After the two preceding experiments, the animal
will live for a considerable time, but if the phrenic nerves,
and the spinal marrow, towards the end of the neck, be
divided at the same time, or what comes to the same
thing, if the spinal marrow be cut above the origin of the
phrenic nerves, then all communication between the brain
and the active agents of respiration is cut off, and death
follows of course.
4thly, I have frequently observed, that half an inch of
difference in the place where the spinal marrow is divided,
produces such a difference in its consequences, that in the
one case the death is sudden, and supervenes in the other
only, after an interval of fifteen or twenty hours. In
dissecting the carcases of animals killed in this manner,
I have constantly observed that the difference depended
always upon the circumstance, of the phrenic nerve being
cut or not.
From these experiments then it is evident, that respiration
ceases on a sudden, and in the following manner, in
all lesions of that part of the nervous system, which is
placed above the origin of the phrenic nerves. 1st,
There is an interruption of action in the voluntary nerves,
which are placed below the point of lesion, and consequently
in the phrenic and intercostal nerves. 2dly, A
paralysis of almost all the muscles of the animal life, and
particularly of the diaphragm and intercostal muscles.
3dly, A cessation of the mechanical phenomena of respiration.
4thly, A suspension of the chemical phenomena
of respiration. The interruption of all these movements,
is as rapid as their concatenation is prompt, in the natural
order.
It is thus that those persons perish, who experience any
great lesion of the spinal marrow, between the brain and
the origin of the phrenic nerves. Physicians have been
very much embarrassed, in fixing with precision the spot,
when a wound of the medulla ceases to be mortal; from
what I have advanced, the limit is easily assigned.[113] From
the same causes, concussion, and compression of the brain,
are also fatal.
We should observe notwithstanding, that these different
causes of death, may act with various degrees of intensity.
If they act but feebly, they affect the intellectual functions
only, for these functions are always the first to be
altered, in all lesions of the brain however small. If the
lesion be greater, the affection extends to the muscles of
the limbs, and convulsion or palsy ensue. Lastly, if the
lesion be very great, the whole of the muscles of the
animal life, the intercostals and diaphragm, as well as
the others, are paralyzed, and death follows.
We now can reply to the question proposed at the
beginning of this section, and affirm that the death of
the lungs is occasioned indirectly, by the death of the
brain.
It follows also, from the principles which are above
established, that respiration is a mixed function, a function
placed as it were between the two lives, to which it
serves as a point of contact, belonging to the animal life
by its mechanical functions, and to the organic life, by its
chemical functions; and hence we have the reason no
doubt, why the existence of the lungs is as much connected
with that of the brain, as with that of the heart.
It may be observed in the series of animals, that in
proportion as the organization of the brain is straitened,
a number of the phenomena of respiration also are lost.
In birds, and the mammalia, this function as well as the
brain, is much more developed than it is in the classes of
fish and reptiles. It is known, that the nervous system
of those animals which breathe by tracheæ, is less perfect
than in those which breathe by lungs; and that in those,
where there is no nervous system, that of respiration
disappears also.
In general, there is a reciprocal relation between the
brain and the lungs, especially in birds and the mammalia.
The first of these occasions the action of the second, by
raising the ribs and favouring the entrance of air into the
bronchiæ; the second also keeps up the activity of the
first, by means of the red blood which it sends thither.
It would be an interesting speculation to inquire into
the relation of the nervous system with that of respiration
in the class of insects, for as they receive the air
by points, which open externally, there seems to be no
mechanical action in the process of their breathing, and
thus the function appears with them to belong entirely to
the organic life.
In the preceding chapter we have shewn how the lungs
remain inactive, when the brain ceases to act.—The same
phenomenon, under the same circumstances, takes place
also in the heart, and must happen either immediately or
mediately.
The greater number of medical men, speak in much
too vague a manner of the cerebral influence. They
do not sufficiently determine its extent and limits, with
respect to the different organs of the system.
It is evident that we shall have answered the question
proposed at the head of this section, if we can determine
what the influence of the brain is with regard to the heart.
Now, we have every reason to suppose, that no direct
influence is exercised by the former over the latter of
these organs, which, on the contrary, is immediately
dependent with regard to its operations, on the movement
communicated to it by the blood. This assertion is by
no means a new one. It has been admitted by all sound
physiologists; but as many opinions in medicine are
founded upon a contrary principle, it will not be amiss to
dwell upon it a little. It is equally demonstrated both
by observation and experiment—and to begin with the
former:
1st, All violent irritation made upon the brain, produces
either partial, or general convulsion in the muscles
of the animal life. Examine those of the organic life,
on the contrary, and little will be found amiss in their
actions.
2dly, All compression of the cerebral mass, whether
made by pus, water or blood, has ordinarily the effect of
paralyzing the voluntary muscles; but so long as the
affection does not extend to the muscles of the breast, the
action of the heart is in no degree diminished.
3dly, Opium and wine, when taken in a certain quantity,
diminish the cerebral energy for the moment and
render the brain unfit for the functions of the animal life.
The action of the heart, on the contrary, is increased.
4thly, In palpitation, and the different irregular movements
of the heart, it is not observable that the principle
of these derangements exists in the brain.—In this respect,
as well as on the subject of syncope, Cullen has been
mistaken. The brain during such time, continues in
action as usual.
5thly, The numerous phenomena of apoplexy, and
epilepsy, and concussion, &c. do certainly all of them tend
to shew, how independent the heart is of the brain.
6thly, Every organ which is subject to the direct influence
of the brain, is for that very reason an organ of
volition. Now, I should suppose, that few persons of the
present day, would be inclined to maintain with Stahl,
that the heart is among the number of such organs.
What would life be, were we able at will, to suspend the
action of the organ, by which the system is animated?
From simple observation, then, we might conclude, that
it is not immediately that the heart ceases to act, when
the functions of the brain are interrupted, but this fundamental
datum of physiology and pathology, we shall
further establish, upon actual experiment.
1st, If the brain of an animal be exposed, and irritated
either with mechanical or chemical agents, a variety of
alterations will, indeed, be produced in the organs of the
animal life, but none in the heart, so long as the muscles
of the breast continue to perform their functions.
2dly, Experiments made in the same manner upon the
spinal marrow of the neck, present the same results.
3dly, If the eighth pair of nerves be irritated, the
movements of the heart will not be accelerated; they will
not be arrested if these two nerves be divided. In all
these experiments, however, we must be careful to make
a proper distinction between the emotions and passions
of the animal, and what it really suffers from the experiment.
4thly, The nature of the great sympathetic nerve, I
suppose to be known;[114] now if the same experiments be
made on the cardiac branches of this nerve, as were made
upon the eighth pair, the same results will follow.
I do not offer in detail the whole of these experiments;
the greater part of them are well known: I was induced
to repeat them, as authors are not agreed upon their consequences.
The experiments of galvanism, are well calculated to
throw light upon the relations existing between the heart
and the brain; these I have taken care to repeat with
the utmost exactness, and whatever authors may have
advanced, they are all in favour of the above opinions—for
1st, If the galvanic apparatus be applied to the brain,
and to the heart, and inferior extremities of a frog, and
the communication made between the metals, there will
constantly be seen a strong contraction in the muscles of
the limb, and little or none in the heart. The same will
be the case, to whatever voluntary muscle the zinc be
applied. 2dly, The same results will be had, on the
communication being made between the metals applied
on the one hand to the spinal marrow above the giving
off of the sympathetic, and on the other hand to the heart,
and any of the voluntary muscles.
3dly, On establishing a communication between the
metals applied to the cardiac nerves, and to the heart of
the animal, there has been no contraction in the heart.
In all these essays, the natural disposition between the
parts which serve to unite the two organs, is preserved:
there are other experiments which consist in detaching
the heart from the breast. 2dly, In placing two points of
its surface in contact with two different metals. 3dly, In
making the communication between them with a third.
From this experiment, Humboldt and other philosophers
have procured contractions, but I have taken care to
repeat it with the greatest accuracy, and must assert,
that I have seen little or nothing of the kind; indeed,
if I had, I should have concluded nothing from it;
for it appears to me, that to decide upon the influence
of the brain over the heart, a portion at least of the
nervous system, should be in contact with one of the
metals.
I shall now pass to my experiments on red and warm-blooded
animals. They are necessary for the decision of
the question before us, as the mode of contractility in
these animals differs much from that of the animals submitted
to the experiments already mentioned.
1st, In the winter of the year 1798, I was authorized
to make different essays on the bodies of persons who
had been guillotined. I had them at my disposal thirty
or forty minutes after they had undergone the punishment.
In some of them, all mobility was extinct; in others,
this property could be reanimated in all the muscles by
the common agents, and in those of the animal life, by
galvanism especially.[115] Notwithstanding which, I could
never occasion the least motion, in applying the apparatus
either to the spinal marrow and the heart, or to this
latter organ and the nerves, which it receives from the
ganglions of the sympathetic, or the par vagum. Nevertheless,
the common mechanical excitant, immediately
applied to the fleshy fibre, occasioned its contraction.
Could this have happened in consequence of the separation
of the nervous fillets from the brain? assuredly not;
because the voluntary muscles were equally separated
from it, and yet affected strongly. If any doubt remain,
the following experiments will clear it up.
2dly, In dogs and guinea pigs, I have repeatedly applied
the metals, first to the brain and the heart, then to the
trunk of the spinal marrow, and the heart; then to the par
vagum and the heart. The communication being made,
was followed by no apparent result.
3dly, On making the communication between the
metals, when applied to the cardiac nerves and the heart,
there was no very sensible motion.
4thly, Humboldt has asserted, that when the heart is
speedily detached with some of its nervous threads about
it, a contraction may be excited, by arming the nerves
with a metal, and then by touching this metal with another.
I have many times tried this experiment in vain. I confess,
however, that once it appeared to me to succeed.
5thly, On the contrary, I have almost always succeeded
in producing contractions in the heart, by cutting
it away from the breast, and making a communication
between a couple of metals, applied to different points of
its surface. This, if I am not mistaken, is the only means
of evidently producing the phenomena of galvanism in
this organ, but with respect to our present question, the
experiment is wholly inconclusive.
All these experiments I have repeated many times, and
with the most scrupulous precautions, nevertheless I do
not pretend to call in question the reality of those results,
which other physicians have remarked. It is well known
how very variable those experiments are, which have the
vital powers for their object. Besides, in admitting even
these different results, I do not see how it is possible to
refuse acknowledging, that with respect to the stimulus
of galvanism, there is a wide difference between the
susceptibility of the muscles of the animal life, and those
of the organic life. Again, supposing that the galvanic
phenomena were the same in both sorts of muscles, the
fact would prove nothing more, than that these phenomena
with regard to their succession, follow laws directly the
contrary of those, which are displayed in the phenomena
which take place, when any common cause of irritation
is applied to the nerves and their corresponding muscles.
The proofs adduced, will allow us to conclude, that the
brain exercises no direct influence over the heart, and
consequently, that when it ceases to act, the functions of
the latter must be interrupted indirectly.
When the brain dies, the heart dies, but not directly.
There must be some intermediate organ then, the death
of which occasions that of the heart.[116] That intermediate
organ is the lungs. In this sort of death, the following
is the series of the phenomena which may be observed.
1st, The cerebral action is interrupted. 2dly, The
action of all the muscles of the animal life, and consequently
of the intercostals and diaphragm, is annihilated.
3dly, The mechanical functions of the lungs are suspended.
4thly, The like ensues with respect to their chemical
functions. 5thly, The fibres of the heart are penetrated
with black blood. 6thly, The fibres when so penetrated,
die.
Such sort of death then, has much resemblance with that
which is occasioned by the different asphyxiæ. It is only
more sudden, and that for reasons which I shall presently
point out. The following experiments are an evident
proof that the phenomena take place as I have described
them to do.
1st, I have always found black blood in the red-blooded
system of all animals, killed by concussion or compression
of the brain; the heart livid, and the different surfaces
coloured as in asphyxia.
2dly, I opened the carotid artery of a dog; the red
blood instantly gushed out, but was immediately suppressed,
and the artery tied. I then killed the creature, by
striking him with violence on the occipital bone.[117] The
animal life, and consequently both the mechanical and
chemical functions of the lungs, were suddenly suppressed.
The artery was then united. It poured forth the black
blood with a feeble jet, for some little time, and after some
minutes, the heart entirely ceased to move.
3dly, I have always obtained a similar result in opening
the arteries of different animals which I afterwards
killed, either by dividing the marrow between the first
vertebra and occiput, or by strongly compressing the
brain, which I had previously exposed.—It is thus also
that animals perish, by the carotids of which a deleterious
substance has been injected.
4thly, The preceding experiments explain the reason
why the blood is black which flows from the arteries of
animals, which are bled in our slaughter-houses, after
having been knocked in the head. If the blow has been
violent, the blood issues such as it was in the veins, but
if the action of the diaphragm and intercostals has only
been weakened by the blow, the redness of the blood is
only diminished.
The state in which the respiration may be (and it is
altered from a variety of circumstances during profuse
hemorrhagy) occasions a great variety in the colour of the
arterial blood: hence we have the reason why it is found
of so many different shades in the great operations of
surgery. At the beginning of these, it often flows out
quite red; at the end of them, is sometimes almost black.
The easy or embarrassed state of the respiration of the
patient, is the occasion of these varieties. This I have
frequently remarked, when attending Desault, and was
often struck with the appearance, before I knew the cause
of it.
I have never found any relation whatever, between the
obscure colour of the blood, and the compression exercised
above the artery, as some have asserted to take place.
There is, indeed, a connection between the colour and
the impetuosity of the jet, but the reason of this is evident
to any one who has read the foregoing pages.
To return to the point of doctrine on which we are at
present occupied, I am persuaded from the considerations
and experiments which are adduced in the course of this
chapter, that the manner in which the heart ceases to act,
when the cerebral functions are suspended, can no longer
admit of a doubt, and that we may resolve the question
proposed, in affirming that under such circumstances, the
death of the heart is occasioned through the medium of
that of the lungs.
There is this difference, then, between the death of the
heart, in consequence of that of the brain, and the death
of the brain in consequence of that of the heart, that the
one is indirect, the other direct, as we have already seen.
If some men, as Stahl asserts, have really been able to
suspend the movements of the heart, the fact is not a
proof of the influence of the mind over the muscles of the
organic life, but of its power over the mechanical, and
consequently, the chemical phenomena of respiration.
In red and cold-blooded animals, the death of the heart
does not succeed the death of the brain so quickly as it
does in red and warm-blooded animals. Cut off the head
of a frog, and the heart will continue to beat for some time
afterwards. This phenomenon will be easily accounted
for, if we recollect that respiration with these animals
may be suspended a length of time, without arresting the
movements of the heart.
In fact, as the heart dies only because the lungs die in
the first place, when the cerebral functions are interrupted,
it is plain that there ought to exist between the violent
death of the heart and that of the brain, an interval nearly
equal to that during which, in the natural state, there may
be a suspension of respiration.
When the brain dies, the animal life dies, for the
functions of this life, either directly or indirectly, have
their seat in the brain. It is manifest, that all the operations
and affections of the mind, together with sensation,
locomotion, and the voice, must be put an end to in such
case. The difficulty then respects the functions of the
organic life.
We shall here adduce both observation and experiment
to prove, that the internal functions are all of them, as well
as the action of the heart, withdrawn from the immediate
influence of the brain.
1st, There are a number of diseases affecting the brain,
which occasion so general a suspension of the animal life,
as to leave neither sensation nor voluntary motion, excepting
some feeble oscillations of the intercostals and the
diaphragm. In this state the individual has lost the half
of his existence, but the one half composed of the organic
functions, continues in the meanwhile to subsist, and in
many cases with energy. This phenomenon is exemplified
continually in apoplexy, in concussion of the brain,
and extravasation of blood upon its surface.
2dly, During sleep the secretions certainly go on,
though Bordeu insists upon the contrary opinion, with
the view of proving the influence of the nerves over the
glands. During a state of sleep, digestion goes on as
usually it does. The exhalations of the body are made
with perfect freedom, and often augmented beyond their
natural quantity; the process of nutrition continues to
be effected, and is probably under such circumstances,
increased. There are many proofs in favor of this opinion;
but a state of sleep is a state of collapse in the brain.
Then, neither is the relaxation of the functions of the
internal organs the consequence of a relaxation of action
in the brain, nor the death of the former the immediate
effect of the death of the latter.
3dly, The sleep of animals, which pass a certain part
of the year in a state of torpor, is a very strong proof of
the co-existence of a suspension of the cerebral functions,
with a permanent action of those of the organic life.[118]
4thly, In the different palsies; in those for instance
which affect the lower limbs, and the viscera of the pelvis,
in consequence of some concussion or compression of the
medulla spinalis, the communication of the paralyzed
parts with the brain, is either entirely cut off, or only
enfeebled. It is entirely interrupted when all feeling and
power of moving have ceased—it is enfeebled, when the
one and the other of these properties are only enfeebled.
But in these two cases the general and the capillary circulations
continue. The exhalations from the cutaneous
surface and in the cellular substance, are made as usual;
the process of absorption goes on, for without absorption,
we should soon see dropsy. The secretions also are
effected, for nothing in such sort of palsy is more common
than a copious secretion of mucus from the bladder. As
for nutrition if it be diminished in energy, the process is
certainly never entirely arrested.
5thly, Spasms and convulsions, which proceed from an
unnatural energy of the cerebral action, have little influence
over the exhalation, secretion, and nutrition of the
parts in which they make their appearance. The trouble
and excessive agitation of the animal life of such parts,
compared with the calm of their organic life, are facts
well worthy of remark.
6thly, Fœtuses without heads, in the uterus, possess as
active an organic life, as those which have no defect of conformation
whatever, and sometimes at the time of birth,
are monstrous even in bulk; this circumstance I have
frequently had occasion to observe at my amphitheatre;
the functions of nutrition then and circulation may take
place with activity, though deprived of the influence of
the brain:
7thly, In animals, which have no cerebral mass, and in
those (the polypes for instance) where not even a nervous
system is apparent, these organic processes are admirably
well conducted,[119] the greater part of them indeed are
common to the vegetable, and the animal.
8thly, If the different proofs, which Bordeu has given
of the influence of the brain over the functions be well
examined, it will seem that no one of them is decisive.
The sudden interruption of the secreted fluid, in consequence
of the division of the nerves of the part, would
be the only proof which I should be inclined to admit as
positive. Now I am not acquainted with any means of
making such division with exactness. We have heard
much of an experiment of this nature upon the parotids;
but the disposition of the nerves distributed to these
glands is such, that I have not been even tempted to
repeat the experiment. The testicle is better adapted for
the attempt, and accordingly without touching the vessels,
I divided the spermatic nerves, but an inflammation and a
deposit of matter took place in the gland, and with respect
to the secretion of the semen, I could not judge of the
effect of the division of the nerves. But here this very
inflammation coming on without the influence of the
brain, appears to me to infer a possibility of the seminal
secretion under the same circumstances. In this experiment,
the spermatic artery cannot be separated from the
plexus which it receives from the great sympathetic, so
intricate is the network of these nerves about it; their
division however is of little consequence, as they come
from the ganglions. It is easy to break off all communication
with the brain, by destroying the lumbar fillets of
nerves.
I might add a number of other considerations to the
above, but here I have to remark that the distinction of
the sensibility and contractility into their two kinds is
particularly worth attention. In fact, the idea of sensibility
in our usual way of seeing things, suggests the idea
of the nerves, the nerves again make us think upon the
brain, we associate the three ideas, but excepting for
the animal life they should not be associated. In the
organic life, at least their union is not immediate.
I do not mean to say that the cerebral nerves have no
influence whatever over the organic sensibility, but I
maintain that such influence is not direct and not of the
nature of that which is observed in the animal sensibility.
Many authors have already discovered a number of
difficulties resulting from the opinion which makes the
nerves the exclusive seat of sensibility, they have even
sought for other means of explaining the phenomena of
great living bodies. But of its agents we know as little
as we do of its nature, and have no means of elucidating
questions of this sort. Let us be contented with analyzing,
collecting and comparing facts with seizing their
general results; the aggregate of these researches will
compose the true theory of the vital powers; the rest is
only conjecture: but besides the considerations which I
have offered, there is another which manifestly goes to
prove that the organic functions are not under the immediate
influence of the brain, and this is, that the viscera,
which perform such functions do not receive their nerves
from the brain but from the ganglions.
This anatomical fact is observable in the liver, the
kidney, the spleen, pancreas, intestines, &c. even in the
organs of the animal life there are nerves which serve
for the external, and nerves which serve for the internal
functions. In such the former come directly from the
brain, the latter from the ganglions. Thus the ciliary
nerves, which come off from the opthalmic ganglion, are
those which preside over the secretions and nutrition of
the eyes, the optic nerve which is derived from the brain
is the nerve of vision.[120] In the same way the olfactory
nerves of the pituitary membrane are the agents by which
we have the perception of odours, the threads which come
off from the ganglions of Mekel, relate only to the organic
phenomena of the membranes.
Now the nerves of the ganglions cannot transmit the
action of the brain; for we have seen that the nervous
system derived from these bodies should be considered as
entirely independent of the nervous system of the brain;
and that the great sympathetic does not derive its origin
from the brain, from the spinal marrow, or from the
nerves of the animal life; but from the ganglions exclusively;
this nerve indeed does not exist, it is only the
aggregate of so many small nervous systems as there are
ganglions, which are the particular centres of the organic
life, just in the same way as the brain is the great and
only centre of the animal life.
To establish it as a fact that the great sympathetic such
as it is understood does not in reality exist, I might add a
number of proofs to those, which I have already mentioned.
The nervous communications, which are taken for
it, are nothing more than accessories to the system of the
ganglions; for 1st, These nervous communications, as
Cuvier has observed, are not met with in the necks of
birds; between the upper cervical and first thoracic
ganglion there is no vestige of a sympathetic. In birds
then, the upper cervical ganglion is that which in man
the opthalmic ganglion, the ganglion of Mekel and others
are. This disposition, which is natural in birds, agrees
with what I have sometimes observed in the human subject
between the first lumbar and the last thoracic ganglions,
as well as between the lumbar and sacral ganglions themselves.
2dly, In many instances there are no ganglions
in the spot where the pretended sympathetic nerve communicates
with the spinal marrow. This may be seen in
the human neck, and in the abdomen of fish, but such
disposition should be thus regarded. The inferior cervical
ganglion furnishes a great branch which ascends to
the superior cervical ganglion, and establishes between
the two a direct communication; but in ascending it distributes
many branches to each of the cervical nerves,
which form a secondary communication.
If we reflect on these considerations, together with
those which have been already offered, we shall be more
and more convinced—1st, That the great sympathetic is
only an assemblage of small nervous systems, having each
of them a ganglion for its centre, and all of them independent
of each other, though generally communicating
with the spinal marrow and between themselves. 2dly,
That the nerves belonging to these small systems, cannot
be considered as a part of the great nervous system of
the animal life. 3dly, That the organs, which are provided
exclusively with the nerves, are not under the
immediate influence of the brain.
Notwithstanding which, we must not suppose that all
the organs which serve for the internal functions, receive
their nerves exclusively from the ganglions: many of
these organs are furnished from the brain, and yet from
experiment, it is found that they are not under the immediate
influence of the brain.
As yet we have only observation and reasoning for the
basis of the important principle which we are labouring
to establish, namely, that the organic functions are not
directly put a stop to in consequence of the death of the
brain; but experiments upon living animals are not a less
evident demonstration of this principle.
1st, I have always observed, that in producing palsy
or convulsion, I have never been able to impair in any
very sensible or sudden manner, either the exhalation,
the absorption, or the nutrition of the convulsed or palsied
part.
2dly, It has been for a long time known, that no spasm
of the muscular fibres of the stomach, bladder, or intestines,
can be produced by irritating the nerves of the
ganglions which go to these organs.
3dly, The division of the nerves of the ganglions,
will not immediately paralyze the hollow organs. Their
vermicular motions continue for a long time after the
experiment.
4thly, With respect to the stomach, intestines, bladder
and uterus, I have repeated the galvanic experiments
which, with respect to the heart, have already been mentioned
at length; but never could obtain contractions.[121]
5thly, The same experiments being made upon the
organic muscles, and the great sympathetic nerve of a
dog, there was no contraction.
6thly, The issue of the latter operation may be easily
conceived, according to our manner of regarding things.
In fact, the ganglions, which are situated between the
gastric organs and the nervous trunk of the chest, might
possibly have interrupted the series of the galvanic phenomena.
With a view, then, to remove all doubt of this
kind, I exposed the nerves, which go from the ganglions
immediately to the stomach, bladder and rectum, and in
this way galvanised the organs but no contraction appeared
to me to be the result of the experiment; at least no
contraction, which I could suppose to be the effect of
galvanism, for here I cannot too much recommend a
proper distinction to be made between that which should
be the effect of this fluid, and that which results from the
mechanical contact of the metals.
7thly, These experiments are not easily made upon the
intestines, on account of the tenuity of their nerves; but
as these nerves compose a very perceptible plexus about
the mesenteric artery, the intestine may be galvanized by
surrounding the artery with one of the metals, while the
other is placed under the intestinal tube. This experiment
I have made, but could not obtain any sensible
result.
8thly, The preceding essays were made upon warm
and red-blooded animals. Similar attempts were repeated
on cold and red-blooded animals, but with no effect.
9thly, The nerves which immediately supply the gastric
organs of the frog, are so delicate as to make it an
extremely difficult matter to get them into proper contact
with the zinc: a small contraction of the stomach was,
however, obtained by Jadelot on operating directly on
these nerves; but this contraction was similar, no doubt,
to those which I have so frequently observed in other
experiments, and not to be compared to the astonishing
effects which are observable in the voluntary muscles. I
shall conclude, therefore, that with respect to the galvanic
phenomena, there exists a wide difference between the
muscles of the animal life and those of the organic life.
I have now collected proof enough, I trust, for resolving,
with certainty, the question proposed in the above
chapter, and for establishing it as a fundamental principle.—1st,
That the brain does not directly influence the
organs and the functions of the internal life; and 2dly,
That, therefore, the interruption of these functions, in
case of any great lesion of the brain, is not an immediate
effect of such lesion.
Nevertheless, I am far from considering the cerebral
action as foreign entirely to the organic life. I only
maintain that its influence upon it is indirect, and as yet
but little known. I have been somewhat prolix upon
this subject; for certainly nothing in medicine is more
vague than the sense which is commonly attached to the
words nervous action, cerebral action, &c. There is
never a proper distinction made between that which
belongs to one life, and that which is the attribute of the
other. Cullen, in particular, may be reproached with
having exaggerated the influence of the brain.
The organic life continues to subsist for a certain time,
after the apparent death of the individual. There must
be some intermediate agents then, the cessation of the
action of which, occasions the death of the inward organs.
Such agents are chiefly the mechanical organs of respiration.
The series of the phenomena are the following:
1st, The cerebral actions are interrupted.—2dly, The
mechanical functions of the lungs are put an end to.—3dly,
There is an annihilation of their chemical functions.—4thly,
The black blood circulates in all the parts.—5thly,
The movement of the heart and the action of all
the parts is weakened.—6thly, Suspended.
All the inward organs then, die nearly as they do in
asphyxia; that is to say—1st, Because they are penetrated
by the black blood.—2dly, Because the circulation ceases
to communicate that motion which is essential to their
life.
Nevertheless, there are many differences between death
from asphyxia, and death from lesion of the brain. 1st,
The animal life in the latter sort of death, is generally
interrupted at the very instant of the shock or blow. In
the former it is terminated only in proportion as the black
blood penetrates the substance of the brain.—2dly, In
the greater number of the asphyxiæ, the circulation does
not immediately cease, the blood is only gradually blackened,
and continues for some time to be moved onwards
by the agitation of such parts as are still under the
influence of the brain. On the contrary, in lesion of the
brain, the interruption of respiration is sudden; the blood
also loses its red colour at once: on the other hand, the
animal life being suddenly arrested, the organs of volition
become immovable on the spot, and are capable no longer
of favouring the motion of the blood. This remark is
particularly applicable to the breast, the parietes of which
facilitate very much the pulmonary circulation, and even
the movements of the heart by their rise and fall, for
in such alternation of motion consists the true influence
which the circulation receives from the respiratory process.
But after all, these two sorts of death may be more or
less similar to each other according to the way in which
they happen. The differences which I have pointed out
are by no means general. Thus, when asphyxia is sudden,
as when for instance the air of the lungs is pumped
out with a syringe, there are neither livid spots, or fulness
of the lungs to be met with. The circulation ceases
quickly, and the phenomena of death are such as are
observable when the brain is suddenly destroyed.
On the contrary, if the death of the brain be slow, and
the process of respiration for a certain time continued,
the capillary system of the lungs will be gorged with
blood, and the general capillary system be filled also. The
circulation in such case will be slow to cease, and the
phenomena of death like those of many of the asphyxiæ.
Thus the promptitude or slowness of death, proceeding
from lesion of the brain, will occasion all the differences.
It has been often a question in what way criminals
die, who are hanged. In some, the vertebral column is
luxated, and in others, want of respiration is the cause
of death.[122] But whenever there is luxation, there is at
the same time asphyxia, and in such case asphyxia is produced,
both because the pressure of the cord intercepts
the passage of the air, and because the intercostals and
diaphragm are paralyzed.
From what I have now said, a comparison may be
made between the three kinds of death upon which I
have expatiated. This comparison, according to my
ideas, is of importance: I shall give some features of it.
Generally speaking, there is a greater similarity in the
two modes by which the death of the brain, or that of
the lungs produces the death of the organs, than between
either of these modes, and that, where the death of the
heart is followed by the same effect.
But 1st, There is always black blood in the red-blooded
system, when death begins either by the brain or the lungs.
When the functions of the heart are suddenly suspended,
the arterial system contains a portion of red blood only.
2dly, In the two first cases, the circulation continues
for awhile; in the third, it is immediately suppressed.
3dly, When the death of the organs is a consequence
of the death of the heart, they die, because they cease to
receive that excitement, to which they are accustomed
from the motion of the blood. When their death is produced
by that of the brain or lungs, they die not only
because they lose the excitement above-mentioned, but
because they are penetrated by a fluid which is incapable
of keeping up their actions, &c. The reader will easily
finish the parallel which I have thus begun.
In red and cold-blooded animals, the death of the
organs succeeds much more slowly to that of the brain,
than in red and warm-blooded animals. We cannot assign
the reason of this fact, because we do not know the difference
of the arterial blood from the venous blood of these
animals, nor the effect which is produced on their organs
by the contact of either sort of blood with them.
When reptiles remain for a length of time under water,
does the arterial blood become black from want of respiration?
is the influx of such blood into their organs,
pernicious or not?[123] or is there a sufficient quantity of
air contained in the large vesicles of the lungs of these
animals to oxydate their blood for a length of time, as
but little blood is capable of passing into the pulmonary
artery, which is only a branch of the aorta. The latter
opinion appears to be confirmed by the experiment of
injecting the lungs of a dog with a large quantity of
air, in which case the blood of the creature is reddened
for a greater length of time. But all these questions,
notwithstanding the essays of Goodwyn, require much
elucidation.
From the consideration of what has been said in the
preceding chapter, nothing can be more easy than to form
an accurate idea of the manner in which the phenomena
of general death, commencing by the brain, are concatenated.
The series is as follows:
1st, The cerebral action is annihilated. 2dly, There
is a sudden cessation of sensation and voluntary motion.
3dly, A simultaneous paralysis of the intercostals and
diaphragm. 4thly, An interruption of the mechanical
phenomena of respiration and the voice. 5thly, An
annihilation of the chemical phenomena of the lungs.
6thly, A passage of black blood into the arteries. 7thly,
A slowness of circulation owing to the influx of such
blood into the arteries, and the absolute immobility of all
the parts, of the intercostals and diaphragm in particular.
8thly, The heart dies and the general circulation ceases.
9thly, The organic life vanishes. 10thly, The animal
heat, which is the product of all the functions, disappears,
11thly, The white organs die.
Though in this kind of death, as well as in the two
preceding kinds, the functions are suddenly annihilated;
the parts retain, for a certain time, a number of the
properties of life. The organic sensibility and contractility,
continue for some time, to be manifest in the
muscles of the two lives; and in those of the animal life,
the susceptibility of being affected by the galvanic fluid
is very great in the muscles of the animal life.
This permanence of the organic properties, is nearly
the same in every case; the only cause which affects it,
is the slowness with which the phenomena of death have
succeeded each other. In every case where their duration
has been the same, whatever may have been the cause of
death, experiments instituted upon these properties, are
attended with similar results; for it is evident that concussion
of the brain, luxation of the vertebræ, the section
of the spinal marrow, apoplexy, compression of the brain,
or inflammation, are all of them causes which are attended
with a like effect.
The same, however, is not the case with respect to the
asphyxiæ produced by the different gases. We have
shown the reason of this in the more or less deleterious
nature of the gases which produce asphyxiæ.
The state of the lungs also, is very various in the bodies
of persons who have died from lesions of the brain.
This organ is sometimes gorged and sometimes almost
empty: it shews, however, whether the death of the
individual has been sudden or gradual. The same indication
may be had from the state of the exterior surfaces.
The death, which is the consequence of disease, commences
much more rarely in the brain, than in the lungs.
Nevertheless, in certain paroxysms of acute fever, the
blood is violently carried to the head, and is the occasion
of death. The concatenation of its phenomena, are then
the same as take place in sudden death.
There are a great number of other cases besides those
of fever, where the commencement of death may be in
the brain, though the brain itself may not have been
previously affected by the disease. In these cases, the
state of the lungs is very various; but little can be learnt
from it with respect to the nature of the disease. It is
only an indication of the manner in which the functions
have been terminated.
TRANSCRIBER’S NOTE
Footnote [28] is referenced from Footnote [27] not from the text itself.
Footnote [101] is referenced from Footnote [100].
Footnote [108] is referenced from Footnote [107].
Obvious typographical errors and punctuation errors have been
corrected after careful comparison with other occurrences within
the text and consultation of external sources.
Except for those changes noted below, all misspellings in the text,
and inconsistent or archaic usage, have been retained. For example,
air-cells, air cells; economy, œconomy; no-wise, nowise, no wise;
errors, errours; mechanicians; contractility; hemorrhagy; hebetate.
In the main text:
Pg 17, ‘not of the mattter’ replaced by ‘not of the matter’.
Pg 20, ‘its accessaries’ replaced by ‘its accessories’.
Pg 25, ‘TH TWO LIVES’ replaced by ‘THE TWO LIVES’.
Pg 33, ‘make a differerence’ replaced by ‘make a difference’.
Pg 36, ‘at the expence’ replaced by ‘at the expense’.
Pg 58, ‘nearly analagous’ replaced by ‘nearly analogous’.
Pg 59, ‘sudden alteratian’ replaced by ‘sudden alteration’.
Pg 69, ‘whick Authors’ replaced by ‘which Authors’.
Pg 79, ‘it is succeptible’ replaced by ‘it is susceptible’.
Pg 144, ‘at utterence’ replaced by ‘at utterance’.
Pg 149, ‘then the nutrive’ replaced by ‘then the nutritive’.
Pg 173, ‘physiolgist. Now’ replaced by ‘physiologist. Now’.
Pg 173, ‘is ther esult’ replaced by ‘is the result’.
Pg 176, ‘the body ensuses’ replaced by ‘the body ensues’.
Pg 196, ‘which its practicles’ replaced by ‘which its particles’.
Pg 213, ‘cut the treachea’ replaced by ‘cut the trachea’.
Pg 235, ‘is propogated from’ replaced by ‘is propagated from’.
Pg 236, ‘Ex-riments upon’ replaced by ‘Experiments upon’.
Pg 240, ‘to the concominant’ replaced by ‘to the concomitant’.
Pg 248, ‘the venons system’ replaced by ‘the venous system’.
Pg 252, ‘when the functious’ replaced by ‘when the functious’.
Pg 258, ‘swells and cantracts’ replaced by ‘swells and contracts’.
Pg 259, ‘pipe, then when’ replaced by ‘pipe, than when’.
Pg 261, ‘that livid tin’ replaced by ‘that livid tint’.
Pg 278, ‘in sulphureted’ replaced by ‘in sulphurated’.
Pg 278, ‘azot, in pure’ replaced by ‘azote, in pure’.
Pg 293, ‘extensive hemorhagy’ replaced by ‘extensive hemorrhagy’.
Pg 293, ‘have began in’ replaced by ‘has begun in’.
Pg 310, ‘I was authorzied’ replaced by ‘I was authorized’.
Pg 333, ‘of accute fever’ replaced by ‘of acute fever’.
In the Footnotes:
FN 4 (Footnote [4] referenced from) pg 12, ‘the maunmalia’ replaced by ‘the mammalia’.
FN 5 pg 17, ‘opake colour’ replaced by ‘opaque colour’.
FN 5 pg 17, ‘cogulum of milk’ replaced by ‘coagulum of milk’.
FN 13 pg 43, ‘In somnambulition’ replaced by ‘In somnambulism’.
FN 15 pg 57, ‘perfect iudifference’ replaced by ‘perfect indifference’.
FN 27 pg 90, ‘and peritoreum’ replaced by ‘and peritoneum’.
FN 31 pg 105, ‘the duoderum’ replaced by ‘the duodenum’.
FN 31 pg 105, ‘as the ileo-coecal’ replaced by ‘as the ileo-cecal’.
FN 34 pg 118, ‘to the indiosyncrasy’ replaced by ‘to the idiosyncrasy’.
FN 76 pg 206, ‘name of hypocondria’ replaced by ‘name of hypochondria’.
FN 90 pg 236, ‘vena porta, as’ replaced by ‘vena portæ, as’.
FN 92 pg 241, ‘soon ofter grew’ replaced by ‘soon after grew’.
FN 92 pg 241, ‘the plantive cries’ replaced by ‘the plaintive cries’.
FN 103 pg 281, ‘prot-phosphuretted’ replaced by ‘proto-phosphuretted’.
FN 115 pg 311, ‘of middle heighth’ replaced by ‘of middle height’.