The general muscular system very evidently forms
two great divisions, differing essentially from each other,
by the vital forces that animate them, by their external
forms, by their mode of organization, and especially by
the parts they perform, the one in animal life, and the
other in organic. We shall not then consider them together.
Let us begin by the examination of the muscles
of animal life; these are spread out in great number in
the human body. No system as a whole, is of more
considerable size; no one occupies more space in the
economy. Besides the numerous regions that the muscles
fill, they are generally spread out under the skin, and
partake, as it were, of the functions of this organ, protect
like it the subjacent parts, like it bear with impunity
the action of external bodies, and can even be divided
in a more or less considerable extent, without the
general functions of life suffering from it; which renders
them very fit to defend the deep-seated organs, whose
lesion would be very injurious.
From their external forms, the muscles may be divided,
like the bones, into long, broad and short. Their
arrangement varies according to these three general
forms.
The long muscles occupy in general the limbs, to the
conformation of which theirs is accommodated. Separated
from the skin by the aponeuroses, from the bone
by the periosteum, they are situated in a sort of fibrous
gutter, which retains them powerfully, and in which they
are arranged in layers more or less numerous, the deep
ones are confined in their place by the superficial ones,
which, in their turn, have the aponeuroses to support
them. These last are very long; they commonly belong
to the motions of three or four bones and even more,
examples of which we have in the sartorius, the semi-tendinosus
and membranosus, the biceps, the flexors and
the extensors. As they become deeper, they are also
shorter and generally destined to the motions of two
bones only, as the adductors, the pectineus, &c. are a
proof.
Cellular layers separate them; they are loose where
great motions take place, more compact where these motions
are less, very thick where vessels and nerves go
between the muscular fasciculi. Often spaces more or
less considerable, filled with cellular texture, separate
these fasciculi from each other. We divide the long muscles
into simple and compound. They are simple when
a single fasciculus forms them, compound when they arise
from the union of many. These fasciculi are found then
in two different manners; sometimes in fact its division
is at the top of the muscle, as we see in the brachial and
femoral biceps; sometimes it is at the inferior part, at the
most moveable side that this division is met with, as in
the flexor and extensor muscles of the leg and the fore-arm.
The long muscles often separate from each other, are
sometimes held together by means of aponeuroses, which
confound a more or less considerable portion of two, three
and even four of these neighbouring organs. The origin
of the muscles of the internal and external tuberosities
of the humerus exhibits this arrangement, whence results
an essential advantage in the general motions of the limb.
Then in fact the contraction of each muscle serves, both
to cause a motion below in the moveable part to which
it is attached, and to strengthen above the fixed point of
the neighbouring muscles which contract at the same
time with it.
Every long muscle is in general thicker in its middle
than at its extremities, a form which arises from the manner
of the insertion of the fleshy fibres, which arising
above and terminating below, some successively below
others, are so much the less numerous as we approach
nearer each extremity, whilst in the middle they are all
found in juxta-position. The anterior rectus, the long
supinator, the external radial muscles, &c. have manifestly
this arrangement.
There is a particular kind of long muscles, which has
no analogy but in external appearance with that of the
muscles of the limbs. They are those that are embedded
in front and especially behind the spine. Though they
appear simple at first view, these muscles have as many
distinct fasciculi as there are vertebræ. The transversalis
colli, the sacro-lumbalis, the longus colli, &c. represent
very well an elongated fasciculus like the sartorius, the
anterior rectus of the thigh, &c.; but the structure of this
fasciculus has nothing in common with that of these
muscles; it is a series of small fasciculi, which have each
their distinct origin and termination, and which appear
to be confounded into one muscle only because they are
in juxta-position.
The broad muscles occupy in general the parietes of
the cavities of the animal economy, those of the thorax
and abdomen especially. They form in part, these
parietes, defend the internal organs, and at the same time
by their motions assist their functions.
Their thickness is not great; most of them appear like
muscular membranes, sometimes arranged in layers, as in
the abdomen, sometimes covering the long muscles, as on
the back; they are in the first case, much more extensive
superficially than deeper seated.
Whenever abroad muscle arises and terminates on one
of the great cavities, it preserves everywhere nearly its
breadth, because it has a large surface for its insertion.
But if from a cavity it goes to a long bone, or to a small
apophysis, then its fibres gradually approximate; it loses
its breadth, increases in thickness, and terminates in an
angle which is succeeded by a tendon, which concentrates
into a very small space fibres widely scattered on
the side of the cavity. The great dorsal and pectoral
muscles present us an example of this arrangement, which
is met with also in the iliacus, in the glutæi medius and
minimus. The broad muscles of the pectoral cavity have
a peculiar arrangement which the ribs require; their origin
takes place by serrated points fixed to these bones,
and separated by spaces between them.
The broad muscles are most often simple; many rarely
unite to form compound ones. Different cellular layers
separate them, like the long muscles; but they are hardly
ever like them covered by aponeuroses; the greatest number
is merely subjacent to the integuments; the reason is
that their form naturally protects them from these displacements,
of which we have spoken in the article on
aponeuroses, and which, without these membranes, would
be so frequent in the long muscles. I do not know that
the cramp has ever been observed in those of which we
are treating. When the abdominal muscles are laid bare
by incisions made through the integuments of a living
animal, I have observed, that in contracting, the bulk of
each preserves the same place.
The short muscles are those in which the three dimensions
are nearly equal, having a thickness in proportion
to their width and their length. They are found in general
in the places, where is required on the one hand
much power, and on the other small extent of motion;
thus around the temporo-maxillary articulation the masseter
and pterygoids, around the ischio-femoral the quadratus
the gemini the obturators, &c. around the scapulo-humeral
the supra-spinalis and the teres minor, in the
hand the muscles of the palmar eminences, in the foot
various fleshy fasciculi, in the vertebral column the interspinal,
in the head the small and great anterior, posterior
and lateral recti, exhibit more or less regularly the
form of which we are treating, and answer the double
object that I have indicated, on the one hand by the very
considerable number and on the other by the shortness
of their fibres.
The short muscles are, more often than the broad,
united to each other, either in their origin or termination,
as we see in the foot and the hand. Sometimes
they are of a triangular form, as in these two parts;
sometimes they approach to the form of a cube, of which
there is an example in the masseter and pterygoid muscles.
In general they are rarely covered by aponeuroses,
undoubtedly because the shortness of their fibres prevents
them from being liable in a great degree to considerable
displacements.
Besides, the division of the muscles into long, broad
and short, is, like that of the bones, subject to an infinite
number of modifications. In fact many of these organs
have mixed characters; thus the sub-scapularis and the
infra-spinalis have a form intermediate to the broad and
short one; thus the cruræus, the gemelli of the leg,
&c. cannot be considered precisely long or broad muscles.
Nature varies, according to the functions of the
organs, the conformation of the agents of their motions,
and we can only establish approximations in our anatomical
divisions.
The part peculiar to a muscle is what is commonly
called the muscular fibre; the vessels, the nerves, the
exhalants, the absorbents and the cellular texture, which
is very abundant around this fibre, form its common parts.
The muscular fibre is red, soft, of an uniform size in
the great and small muscles, sometimes disposed in very
evident fasciculi and separated from each other by remarkable
grooves, as in the gluteus maximus, the deltoid, &c.
sometimes more equally in juxta-position, as in most of
the broad muscles, always united to many others of the
same nature like it, easily by this union distinguished by
the naked eye, but eluding microscopic researches when
we wish to examine it in a separate manner, so great is
its tenuity. Notwithstanding this extreme tenuity, an
infinite number of researches have been made during the
last age, to determine with precision the size of this fibre.
On this point may be read the result of the labours of Leuwenhoek,
Muysk, &c. I shall not give here this result,
because science can draw nothing from it, and because we
cannot rely upon its accuracy; of what importance moreover
is the precise size of the muscular fibre? its knowledge
would add nothing to our physiological views upon
the motion of the muscles.
Every muscular fibre runs its course without bifurcating
or dividing in any manner, though many have thought
otherwise; it is found only in juxta-position to those
which are near it, and not intermixed, as often happens
in the fibrous system; an arrangement that was rendered
necessary by the insulated motions it performs; for the
general contraction of a muscle is the union of many partial
contractions, wholly distinct and independent of each
other.
The length of the fleshy fibres varies very much. If
we examine in general the mass which they form by their
union, we observe that this mass has sometimes much
greater extent than the tendinous portion of the muscle,
as the biceps, the coraco-brachialis, the rectus internus
femoris, &c.; that sometimes its length is much less as in
the small plantar and palmar muscles, &c.; and that sometimes
it is about equal, as in the external radial, &c.
If from the examination of the fleshy mass, we pass to
that of the separate fibres that compose it, we see that the
length of the first is rarely the same as that of the second.
There are hardly any but the sartorius and some analogous
muscles, whose fibres run the whole extent of the
fleshy, mass; in almost all the others, they are found
obliquely arranged between two aponeuroses, or between
a tendon and an aponeurosis; so that though each of them
may be very short, as a whole they are very long, as we
observe in the anterior rectus of the thigh, the semi-membranosus,
&c. This arrangement may also arise from various
tendinous intersections, which cut at different distances
the length of the fibres. In general, the muscles
which owe their length to long fibres, have great extent
and very little power of motion; whilst those with short
fibres, but multiplied so as to give great length as a whole,
are remarkable for an opposite character. And this is the
reason: all the fibres being equally large, whatever may
be their length, have the same degree of force; it is evident
then that this force considered in a muscle as a whole,
is measured by the number of its fibres. On the other
hand, the longer a fibre is, the more it shortens in its
contraction; then by contracting, a muscle brings its
attachments so much the nearer in proportion as its fibres
are longer.
All the fibres of the voluntary muscles are straight,
those of the sphincters excepted. They are either parallel
as in the rhomboids, or obliquely situated in relation to
each other, as in the great pectoral. Sometimes in the
same muscle many sets cross each other in different directions,
as we see in the masseter; but this crossing is
wholly different from that of the involuntary muscles in
which there is more crossing of fibres, whilst here we see
only fasciculi in different directions, in juxta-position to
each other.
I shall not speak here of the cylindrical form according
to some, and the globular one according to others, of the
fleshy fibre; inspection teaches us nothing upon this
point; how then can we make that an object of research
and give an opinion upon it, which has no real foundation?
Let us say thus much of the intimate nature of this
fibre, upon which so much has been written. It is unknown
to us, and all that has been said upon its continuity
with the vascular and nervous extremities, upon its
pretended cavity, upon the marrow, which according to some
filled it, &c. is only a collection of vague ideas, which
nothing positive confirms, and to which a methodical
mind would not attend. Let us begin to study nature
where she begins to come under our senses. I would
compare the anatomical researches upon the intimate
structure of the organs, to the physiological researches
upon the first causes of the functions. In both we are
without guides, without precise and accurate data; why
then give ourselves up to them?
All that we can know upon the nature of the muscular
fibre, is that it is peculiar, that it is not the same as that
of the nerves, nor as that of the vessels, nor as that of the
tendons or the cellular texture; for where there is identity
of nature, there ought to be identity of vital properties
and of texture. Now we shall see that all these
systems differ essentially from each other in this point
of view; there can be between them no analogy in relation
to their nature, whence the properties are always
derived.
The muscular texture is remarkable for its softness and
small degree of resistance. It is by this that it is essentially
different from the fibrous texture. It breaks with
ease in the dead body. In the living, this rupture is rare,
because the contraction which exists in all the violent
efforts, gives it a density, by which it gains an enormous
increase of resistance, but which it loses when it is no
longer in a state of contraction. There are however examples
of the rupture of muscles; it is principally in the
rectus abdominis and quadratus lumborum that they take
place. I have seen one in this last. Observe that this
muscle and all those placed between the ribs and the
pelvis, are much disposed, from their situation, to these
ruptures. In fact, when the pelvis and the thorax are
carried in an opposite direction, these muscles are so much
the more violently stretched, as in these motions all the
superior part of the body forms with the thorax, a great
lever, which is moved in an opposite direction to another
great lever, which is formed by the pelvis and all the inferior
parts; now from their length, these levers are
capable of receiving a very great motion, of communicating
it consequently to the abdominal muscles which
are stretched between the two, and which serve to unite
them. Hence how in a violent inclination to the right,
the quadratus of the left side can be torn, &c. Observe
that but few of the muscles in the economy are found
between two levers so great, consequently are capable of
being so much distended, and especially of being so with
a force greater than that of their contraction; for every
muscular rupture supposes the excess of the external
motion, which distends, over that of the fleshy fibres
which contract to oppose this distension. If the external
efforts were concentrated upon a single muscle, they
would be able more often to overcome the resistance;
but almost always many partake of the effort to support
and the resistance to oppose.
Composition of the Muscular Texture.
The muscular texture has been with chemists, a more
particular object of research than most of the other organized
textures. They have examined it under all its relations.
I refer to their works, to that of Fourcroy especially,
for all which is not strictly relative to the nature
of this texture, for all which considers consequences not
applicable to physiology, which we can deduce from the
knowledge of the principles that enter into its composition.
Exposed to the action of the air, the muscular texture
is affected in two ways. 1st. It dries, if cut into thin
slices, admitting of the evaporation of the fluids it contains.
Then its appearance is of a dull brown; its fibres
contract, it becomes thinner, hard and brittle. If
replunged into water within some days, even fifteen or
thirty after its drying, it resumes its primitive softness
and form, and has a less deep coloured tinge. The water
that has been used for this softening is more or less fetid,
and similar to that of macerations. 2d. Exposed in too
great a mass to the air, the muscular texture does not
dry, but becomes putrid. Thus in making anatomical
preparations by drying, care should be taken to lessen
the thickness of the fleshy parts, or to arrange them so
that the air can penetrate them everywhere. Putrefaction
is inevitable if the air is moist, if the evaporation of the
fluids is not quick enough to produce drying. When it
becomes putrid, the muscle assumes a green, livid colour;
it exhales an offensive odour. Under the influence of the
same circumstances it becomes putrid much quicker than
the fibrous, the cartilaginous and the fibro-cartilaginous
systems. The odour that it exhales then is also very
different from that of these systems; a phosphoric light
often escapes from it. A mass of putridity, in which all
the fibres have almost disappeared, takes the place of the
muscle, when putrefaction is advanced. This mass of
putridity gradually evaporates in part, and there remains
a dark brown residue, which dries and becomes hard and
brittle, nearly like the muscle dried in the ordinary state,
though the appearance however may be very different.
Exposed to the action of water, the muscle undergoes
different phenomena, according as it is hot or cold. Cold
water takes from it at first its red colour, of which it
appears to dissolve the principle. To effect quickly this
phenomenon, it is necessary to expose the flesh, at first
in thin layers, to the action of water that is often changed,
by placing a muscle for example under a fountain, in the
current of a river, or what is much better, by frequently
expressing the water it imbibes; for if we keep it in a
vessel, its exterior only whitens a little, and the interior
preserves its colour. Water which has been used to
wash a muscle, looks like blood spread out in this fluid;
it contains the colouring matter, a little of the extractive
substance, gelatine, &c. I believe that of all the organs
the muscle is that from which we remove most easily its
colour by artificial means. Ought we to be astonished
after this, if nature varies so evidently and so frequently
this colour by the phenomena of nutrition, as we soon
shall have occasion to remark? Kept in water at a
moderate temperature, the muscular texture remains for
a long time without softening; it finally does, and changes
layer by layer into a kind of putridity very different however
from that which is formed in the open air, as I have
frequently observed in macerating the muscles in a cellar,
the temperature of which is uniform. At other times,
instead of putrefying thus, the muscle is changed, as
Fourcroy has remarked, into a substance like spermaceti;
then its fibre is hard and solid. But all the muscles
when kept in water by no means exhibit this phenomenon.
When it does take place, very often a kind of
reddish product, scattered here and there on the surface
of the muscle, and which is an evident effect of decomposition,
announces and afterwards accompanies this state,
without which also, it often takes place. Maceration in
dissecting rooms frequently exhibits this phenomenon.
When we have taken from the muscles their colouring
substance by repeated washings, there remains a white
fibrous texture, from which we can still extract albumen
by ebullition, which rises in scum, gelatine by suffering it
to grow cold, extractive matter which has a deep colour,
by letting it settle, and some phosphoric salts. When all
these substances have disappeared, the residue of the muscle
is a fibrous substance, of a greyish colour, insoluble in
warm water, soluble in the weak acids, giving out much
azote from the action of the nitric acid, and presenting all
the characters of the fibrin of the blood. It appears, as
Fourcroy has remarked, that this substance is truly the
nutritive substance of the muscle, that which, continually
exhaled and absorbed, contributes to its nutritive phenomena
more than all the others; it constitutes the essence
of the muscle, it especially characterizes it, as the phosphate
of lime is the nutritive characteristic matter of the
bones. Is this substance formed in the blood and carried
from it to the muscle, or is it formed in the muscle by
nutrition, and thence carried to the blood? I know not.
Whichever may be the case, it appears to experience
very great varieties in its exhalation and absorption. The
state of laxity, of cohesion, the thousand various appearances
of the muscular texture, appear to belong in part to
these varieties of proportion. Thus the phosphate of
lime or gelatine, diminished by nutrition, give to the
bones softness or brittleness.
It is in this fibrous and essential portion of the muscle,
that particularly resides the faculty of crisping by the
action of caloric, whether by plunging a muscle into boiling
water, or exposing it to the fire; for this crisping is
as evident in the muscle deprived of its colouring matter,
its gelatine, its albumen, and even a portion of its extractive
substance as in the ordinary muscle. There is in general
a constant relation between the quantity of this fibrous
substance contained in the muscles, and the quantity that
the blood contains of it. In the strong, vigorous, sanguineous
temperaments, as they are called, the muscles are
thick and much more fibrous. In all the slow cachexiæ
in which the blood is impoverished, the pulse small and
feeble and in which muscular nutrition has had time to
share but little of the fibrin of the blood, the muscles are
small, weak, soft, &c. In general, the muscles and the
blood are always in constant relation, whilst other systems
often predominate and whilst this fluid seems to be in less
quantity in the economy.
Exposed for a long time to ebullition, as in common
boiled meat, the muscular texture, still united to the adjacent
organs, and to its common parts, gives, 1st, an albuminous
scum which appears to arise more from the lymph
of the cells than from the muscle itself; 2d, many fatty
drops coming also especially from the cellular texture,
almost foreign consequently to the texture of the muscle,
and which swim on its surface; 3d, gelatine formed
especially by the aponeurotic intersections; 4th, an extractive
substance which colours in part the water in
which it is boiled, gives it a peculiar taste and remains in
part adherent to the flesh to which it communicates a
deep tinge wholly different from that of raw flesh, a tinge
which arises also from the colouring matter of the muscle,
and which moreover changes, when the liquor cools, into
a less deep and even a whitish tinge; 5th, various salts
which contribute much to the taste of the liquor, and the
nature of which chemists have ascertained. These are
the natural phenomena of the ebullition of the muscle.
The more extensive analysis of boiled flesh is not my
province; but what ought not to escape us here, are the
phenomena of which the fibre is the seat, whilst the preceding
products are extracted, whether from it, or the
surrounding textures. These phenomena can be referred
to three periods. 1st. When the water is only tepid, and
even a little above the temperature of the body, it leaves
the muscular texture in the same state, or softens it a little.
2d. When it approaches ebullition and begins to be
covered with an albuminous scum, the texture crisps,
thickens and contracts and gives to the muscle a density
much greater than what is natural to it, and augments
considerably its resistance. I have observed that in this
state the muscles bear much greater weights than in a
natural state. They approximate, if we may so say, that
remarkable density which characterizes them when they
contract in the living body, and which so powerfully
opposes their rupture. This condensation of the muscular
texture, which is prompt and sudden, increases till the
period of ebullition, when it is at its greatest height; it
continues only for a certain time. 3d. Gradually it diminishes,
the fibres soften, and are more easily torn than
in their natural state. This softening, the reverse of the
hardening that precedes, is produced slowly and by degrees.
When arrived to a certain degree, the meat is
rendered fit for the table. Observe that then the muscle
has not returned to the state in which it was found before
the hardening; among other phenomena which distinguish
it, the following is an essential one; it has lost the power
of crisping, of acquiring the horny hardness, from the
action of the concentrated acids, from alkohol or from
caloric. In general it becomes putrid more slowly. Its
putrefaction does not give the same odour. We know
how much its taste differs. The principles it has lost are
undoubtedly one of the great causes of these differences.
When a muscle is exposed to an open fire, as in the
roasting of meat, the albumen is condensed, the gelatine
melts, the fibrin filled with juices softens, the extractive
matter flows in part with the gelatine and the salts held
in solution; it is this that forms the gravy, which is, as
we know, very different from melted fat. The exterior
of the meat remains more dense than the interior; it is
coloured by the extractive substance. The interior loses
in part its natural colour; its consistence, its taste and its
composition even change entirely. The fibres, as in
ebullition, lose the power of contracting and of crisping
from the action of strong stimuli and especially that of
fire.
No part in the animal economy is more easily altered
by the digestive juices than the muscles. Almost all
stomachs can bear boiled meat, whilst many reject other
organs when cooked. Carnivorous animals seize upon the
muscles of their prey in preference to the pectoral and
gastric viscera. Muscular flesh is with most people the
most common aliment, that with which they are never
disgusted; it appears to be the most nourishing of all
those, which are afforded by the different textures of animals;
is it, as it has been said, because it contains the
most azote? Whatever may be the reason, the general
part which the muscular system takes in the digestion of
all carnivorous animals, of man especially, is remarkable.
Yet all the parts of this system do not appear to be equally
agreeable to the taste of animals. It is, for example, a
singular fact, that those bodies which are brought to our
dissecting rooms, and which have been attacked by rats,
are found almost always exclusively gnawed in the muscles
of the face.
Observe in regard to the use of the muscles in digestion,
that it is the portion of the fibrous system which adheres
to them, and forms, as it were, a part of them, I refer to
the tendons, which is the most easily altered by maceration,
by ebullition and by the digestive juices. Observe
also that the great mass which the muscles form in the
body of all animals, of which they are more than one
third, presents to the carnivorous species ample materials
for their nutrition; thus nature, by multiplying these
organs for the wants of the individual which they move,
seems to multiply them also for those of the individuals
which he is one day to nourish. In forming them in
each species, it labours for other species as well as for
this. Who knows if this general design, which observation
finds in the series of all animals, be not the cause of
this remarkable predominance which the muscles have
over the other systems? Who knows, if nature would
not have diminished the powers of the animal mechanism
which are so numerous and so complicated in comparison
with those of artificial machines, who knows if she would
not have simplified the means and given the same results,
if the motions of the animals had been the only object of
the formation of the muscles?
The sex has great influence on the quality of the flesh
of animals. I do not believe that any thing precise is
known as to the nature of the influence which the genital
parts exert upon it; but the following are remarkable
facts upon this subject. The muscles of males are stronger
and better nourished, have more taste, resist boiling
for a longer time, are firmer, &c. Boiling water on the
contrary alters quicker the texture of females; it is more
tender and gives to the liquor a less strong taste. In the
season of sexual intercourse, the muscular system of the
first has a peculiar odour, which often renders it disagreeable
even to the taste. It is an observation that is easily
made in quadrupeds, birds and fishes that are brought to
our tables. Without having as strong an odour, the flesh
of the second becomes at this period soft, flaccid and but
little savoury.
Cellular Texture.
The cellular texture is very abundant in the muscular
system; I know of no system that has a greater proportion
of it. This texture forms a very evident covering
around each muscle. This covering is most commonly
loose, filled with fat, easily distended with air in emphysema
and serum in anasarca. At other times it is more
dense, compact and really arranged like a membrane.
Such, for example, is the case with that which covers the
great oblique muscle of the abdomen, and the dissection
of which on this account, students at first find very difficult.
The other abdominal muscles, the trapezius, the
serratus major and the great dorsal exhibit also this arrangement.
We might say that in this way nature compensated
for the aponeuroses, which are wanting on the
broad muscles of the trunk. Besides, this covering has
only a membranous appearance; it has nothing of its organization,
it disappears in the infiltration in which all
the true membranes remain.
Besides this general covering of the muscle, each fasciculus
has a less covering, each fibre a still less one, and
each smaller one a real though almost insensible sheath.
We can then represent the cellular texture of the muscles
as forming a series of coverings successively decreasing.
These coverings favour the motion of the fibres which
they separate, either by the serum of the cells, or by the
fat they contain, both fluids, by lubricating, allow them
to slip more easily upon each other. Frequently between
these fibres, the cellular texture appears to form a kind
of cross pieces which go at right angles. We see this
arrangement especially in the proper extensor of the great
toe, and in the common extensor, the fleshy fasciculi of
which are broad and delicate when distended. In most
of the thick muscles nothing similar is observed.
The quantity of intermuscular cellular texture is remarkably
variable. In general, in all the broad muscles
and in all the large, long muscles, it is very abundant.
It is less in proportion between the fibres of those of the
vertebral canals. Back of the neck, the splenii, complexi,
&c. have less of it than many others, especially in
the spaces that separate them.
Sometimes very considerable cellular elongations are
found in the middle of the muscles, and seem to divide
them into two; such is that which separates the clavicular
portion of the great pectoral; this has even sometimes
embarrassed anatomists as to the division of these
organs.
The cellular texture in general fixes the muscles in their
position; the art of dissection proves it. The effusions
of pus which often perform the office of the scalpel, render
also very evident this use, which does not prevent
the motion in all directions, that the great extensibility
of the cellular texture allows. The cellular texture not
only fixes the muscles to each other, but it also attaches
each of their fibres to neighbouring ones; it flattens
them when they contract, and elongates them when they
are distended; if they are deprived of it their motions
become irregular and uncertain. I have many times
separated with a scalpel a muscle laid bare in a living animal,
into many small fasciculi; in afterwards making this
muscle contract by the irritation of the medulla, by
means of a stilet introduced into its canal, I have observed
in an evident manner this irregularity of motion.
Cut longitudinally a muscle of an extremity from its superior
tendon to its inferior, so as to divide it into two or
three entirely distinct portions, irritate afterwards one of
these portions, the other or the two others will remain
almost always at rest, whilst a single irritated fibre in a
sound muscle, puts in motion the whole of that muscle.
The section of the vessels and the nerves has no doubt a
little influence upon this phenomenon; but that of the
cellular texture certainly contributes to it also.
In dropsical subjects, the serum of the intermuscular
texture is often reddish; this phenomenon is owing to
the action of this serum after death upon the colouring
substance. I believe that this can take place during life
only with great difficulty. The fat sometimes abounds in
this texture, to such a degree that the fleshy fibres disappear
and the fat only is visible; but oftentimes also the
yellow appearance of the muscular fibres, which is produced
by the absence of the colouring substance, is taken
for this fatty state of the muscles. I have seen the first
state but rarely; the second is extremely frequent; we
are sometimes deceived at first view. But ebullition and
combustion easily prove, that the fat is wholly foreign
to this want of colour of the muscles examined in this
state.
Blood Vessels.
The arteries of the muscles are very apparent; they
come from the neighbouring trunks, penetrate the whole
circumference of the organ, more however towards its
middle, than towards its extremities. They run at first
between the principal fasiculi, then divide and their divisions
go between the secondary fasciculi, subdivide and
wind between the fibres, and finally become capillaries
and accompany the small fibres, in which they deposit by
the exhalant system the nutritive matter. There are but
few organs, which have, in proportion to their size, more
blood than the muscles.
The blood is essentially necessary to support their
excitability, as we shall see; it is that which colours
the muscular texture, but not, as it at first seems, by circulating
in its texture. The circulating or free portion
contributes but little to it. It is the portion combined
with the muscular texture, that which contributes to its
nutrition, that gives it its colour; the following are proofs
of it: 1st. The fibres of the intestines are as much or
more penetrated with the circulating blood, than those of
the muscles of animal life, and yet their texture is evidently
whitish, where these vessels are not found. 2d. Many
animals with red and cold blood, frogs in particular, have
muscles almost white, and yet many red vessels run
through this white texture. 3d. I have observed that in
animals destroyed by asphyxia, the colouring substance
does not change colour, no doubt because it is slowly
combined with the muscle by nutrition; that on the contrary,
if we cut a muscle of these animals in the last moments
of life, whilst the venous blood still circulates in
the arterial system, this blood flows out by black jets
from the muscular arteries, the muscular texture itself
remaining red. This curious experiment, which I have
noticed in another work, is made by producing asphyxia
in an animal by compressing the trachea, or by intercepting
the air in any other way in this tube, whilst we
examine the system of the muscles. When a muscle has
been exposed for some time to the contact of the air, to
that of oxygen especially, its red colour becomes evidently
more brilliant.
The muscular vessels permit under certain circumstances
the escape of the blood they contain; hence different
kinds of remarkable hemorrhages, especially in
scorbutic patients, sometimes in putrid fevers, rarely or
never in those diseases that are characterized by an increase
of vitality. Infiltrated with blood in preternatural
hemorrhages, particularly in false aneurisms, the muscles
lose in part their motion; this happens also in contusions,
in which similar infiltrations are observed.
The veins everywhere follow the arteries in the muscles;
they have the same distributions, and receive from
the contractions of these organs an essential assistance to
their action. The throw of blood is more powerful when
the patient we have bled contracts his muscles, than
when he relaxes them; the fluid is as it were expressed,
as from a wet sponge which is squeezed. The arterial
circulation does not exhibit this phenomenon. I have
observed that if we open the artery of the foot of an
animal, and by the irritation of the nerves, make the
muscles of the leg and thigh, through which this artery
passes before reaching the foot, contract powerfully, the
throw of blood is not stronger than during the relaxation.
I have many times injected the veins of the muscles
of animal life with ease, from the trunks towards the
branches, which makes me believe, notwithstanding what
Haller has said, that in these organs, as in the heart, the
valves are less numerous than in many others. No doubt
the assistance the veins derive from their surrounding
organs supplies the place of these folds, or rather renders
them useless, the weight of the column of blood not
making a great effort against the venous parietes. The
varices of the muscular veins are, as we know, extremely
rare. These veins are of two orders; one accompanies
the arteries and follows the same course, the others are
spread superficially on the surface of the organ, without
having corresponding arteries.
There are absorbents and exhalants in the muscles;
but we can with difficulty trace the first, and the second
cannot be perceived.
Nerves.
Almost all the nerves of the muscles of animal life
come from the brain; the ganglions furnish a few of
them; when this happens, as in the neck, the pelvis, &c.
besides the filaments coming from these nervous centres,
there are always filaments of cerebral nerves; without
this, these muscles would be involuntary. Few organs
receive more nerves in proportion to their size than the
muscles. In general the extensors appear to have rather
fewer than the flexors; but the difference is trifling. It
is true that all the great nervous trunks are in the direction
of flexion, that in that of extension there are only
branches, as we see in the posterior part of the arm, of the
fore-arm, the vertebral column, &c. It is true also that
this remark is likewise applicable to the existence of the
vessels, which are larger and more numerous in the first
than in the second direction; but this greater number of
vessels and nerves arises from this, that there are many
more flexors than extensors, that the first are stronger
and have more numerous fibres; so that each of these
fibres hardly receives more nervous or vascular filaments
in one kind of muscles than in the other. I think that
there is but little foundation for what has been said upon
the difference of the strength of the fibres of the flexors
and of the extensors, upon the predominance of the first,
&c. If these are superior, it is either because they are
more numerous, as in the foot, the hand, &c. or more
advantageously arranged, as in the trunk on which the
abdominal muscles act very far from the point of attachment
to bend the spine, whilst to extend it, the dorsal
muscles exert their action immediately at the side of this
point of attachment, as also in the neck, where the muscles
that draw down the lower jaw and head when this
bone is fixed, are much further from the occipital condyles,
than the muscles which produce extension. Whatever
may be the cause of the superiority of the flexors,
the fact cannot be doubted. 1st. In hysterical convulsions,
in those of infants, in all the spasmodic motions in
which the will has no part, the contractions take place
much more in the direction of flexion than in that of
extension. 2d. In old people the flexors finally become
superior to the extensors; for example, the fingers and
toes are almost uniformly bent. 3d. In all the motions,
the power is always on the side of flexion.
The nerves enter the muscles of the extremities at a
very acute angle, because the nervous trunks are in the
natural direction of these organs. In the trunk, on the
contrary, the nerves going from the spine, the cervical
especially, enter their muscles at almost a right angle or
one less evidently acute; this circumstance is of no importance.
Each branch in the fleshy fibres, is at first
divided and then sub-divided in their interstices, and
afterwards lost in their texture. Does each fibre receive
a small nervous filament? We should be led to believe
so from this observation, that the principal branch being
irritated, all the fibres are put into action, no one remains
inert. But on the other hand, if we irritate one of them,
all move also, which is certainly a sympathetic phenomenon
or one arising from the communication of the cells.
Are the nerves deprived of their cellular coverings,
and do they become pulpy when they enter the muscles?
Dissection has shewn me nothing like it.
There are but few systems in the economy in which
the vital properties and those of texture are found in so
great and evident a degree as in this. It is from the
muscles that examples must be selected to give a precise
and accurate idea of these properties. The physical
properties on the contrary are slightly marked in them;
a remarkable softness characterizes them; there is no elastic
power in their texture; there is but very little resistance
from this texture after death; it is from vitality that
it derives the power that characterizes it in its functions.
Extensibility is manifested in the animal muscular system
under many circumstances. The different motions of
our parts render this property evident. Such is in fact
the arrangement of the muscular system, that one of its
portions cannot contract, without the distension of another.
The thigh being strongly bent, the semi-membranosus,
the semi-tendinosus and the biceps are elongated. The
arm being carried out, the great pectoral is extended,
being raised, the great dorsal and the teres major are
stretched. All the great flexions bring into action this
property in the extensors; all the extensions render it
evident in the flexors. A muscle which is stretched by
its antagonist is in a state purely passive; it is as it were
for a moment abandoned by its contractility, or rather it
possesses it, without its being brought into action; it is
made to obey the motion that is communicated to it.
Observe that in these cases, the distension is confined to
the fleshy portion, and the tendon has no connexion with
it; it remains the same, whatever may be the distance, of
the points of attachment, for these points are nearer or
more remote in the different extensions to which the
muscles are exposed; the longest muscles yield the easiest.
The sartorius, the posterior muscles of the thigh,
&c. exhibit this phenomenon in an evident manner; as
their position is accommodated to it. In general all the
muscles remarkable for their length are superficial, and
go most commonly to two articulations, sometimes even
to three or four, as in the limbs. Now the number
of these articulations renders the space comprised between
the two points of attachment susceptible of very
great variations, which the great extensibility of these
muscles allows. It may be understood from what has
been said above, that it is to the length of the fleshy
fibres and to the whole length of the muscle, that its degree
of extensibility is to be referred. Those in which
many aponeuroses are intermixed, and which derive in
part from these membranes or from tendons their length,
possess less of this property. Hence why, in the same
motions, muscles of the same total length become more
or less short, more or less elongated in their fleshy portion.
Observe however that when on the one hand the
tendinous portion predominates much, and on the other
that it is very delicate, it yields a little, as we see in the
small plantar and palmar muscles.
If from the natural state we pass to the morbid, we
see the muscular extensibility manifested in a much more
evident degree. In the face, the air accumulated in the
mouth, swells it by elongating the buccinators; the various
tumours of this cavity, as the fungous and sarcomatous
ones, often distend the small facial muscles in a manner
which would astonish us, if we considered the naturally
small extent of these muscles which are trebled and even
quadrupled. The muscles of the eye-lids and the eye in
the large carcinomas of that organ, those of the anterior
part of the neck in the great swellings of the thyroid
gland, the great pectoral in large aneurisms or in other
tumours of the axilla, the abdominal muscles in pregnancy,
in dropsy, in the various tumours of the abdomen, &c.
the broad and superficial muscles of the back from wens
that are under them, present us these phenomena of distension
in a remarkable manner. The muscles of the extremities
are less subject to them, because on the one
hand fewer causes develop tumours beneath them, and
because on the other the aponeuroses do not yield so
easily to these phenomena.
Contractility of Texture.
The contractility of texture is carried to the highest
point in the muscles. These organs have a continual
tendency to contraction, especially when by being elongated,
they have surpassed their natural size. This tendency
is independent of the action of the nerves, and of
the irritable property of the muscular texture. It is influenced
by life, but it is not entirely dependent on it; it
depends essentially on the structure of the muscles. The
remarkable phenomenon of the antagonist muscles results
from it. The following is this phenomenon.
Each moveable point of the animal frame is always
between two opposite muscular forces, between those of
flexion and extension, of elevation and depression, of adduction
and abduction, of rotation without and rotation
within, &c. This opposition is a condition essential to
the motions; for in order to perform one of them, it is
necessary that the moveable point should be in the opposite
motion; in order to bend, it is necessary that it
should be first extended, and reciprocally. The two opposite
positions which a moveable part takes, are for it
alternately the point of departure and the point of arrival;
the two extremes of these positions are the two limits between
which it can move. Now between these limits there
is a middle point; it is the point of rest of the moveable
part; when it is found there, the muscles are in their natural
state; when it passes it, some are extended, others
are contracted, and such is their arrangement, that the
contraction and extension which take place in an opposite
direction, are exactly in direct ratio. Hence, in the reciprocal
influence that the muscles exert upon each other,
they are alternately active and passive, power and resistance,
organs moved and organs which move. The effect
of every muscle which contracts is not then only to act
upon the bone in which it is inserted, but also upon the
opposite muscle. Between two muscles thus opposed,
there is often no solid intermediate organs, as in the lips,
the linea alba, &c. The muscle of one side acts then
directly upon that which corresponds to it, in order to
distend it. Now this action of the muscles upon each
other is precisely the phenomenon of the antagonists;
two muscles are such when one cannot contract without
elongating the other and vice versa. Let us examine in
this phenomenon the part of the contractility of texture;
it is necessary to distinguish its influence from that of
the vital forces, which has not been heretofore sufficiently
done.
A muscle once placed in the middle position, can only
be removed from it by the influence of the vital forces,
by the animal or sensible organic contractility, because
in this position the contractility of texture of its antagonist
is equal to its own, and there is consequently required
a force added to this to overcome that which is
opposed to it. But if the muscle is found in one of the
two extreme positions, for example in adduction, abduction,
flexion, extension, &c. then there will be an inequality
of action in the antagonists, as it respects the contractility
of texture; the one most stretched, will make
in order to contract itself, an effort much greater than
that which is already contracted. To maintain the equilibrium,
it is necessary then that the vital forces continue
to influence the contracted muscles. Thus every extreme
position of the limbs and of any moveable part, cannot in
an ordinary state be supported except by the influence of
the vital forces. When these forces cease to be in action,
immediately the contractility of texture of the elongated
muscle, which had a tendency to exert itself, but
was prevented, exerts itself, becomes efficacious, and
draws back the moveable part to the middle position, a
position in which the equilibrium is restored. Hence
why in all the cases in which the cerebral influence has
no power over the muscles, in which they are not irritated
by stimulants, the limbs are uniformly found in a
medium position between extension and flexion, abduction
and adduction, &c. This is the case in sleep, in the
fœtus, &c. I have shewn elsewhere how the osseous
arrangement of each articulation is adapted to this phenomenon,
how every kind of relation between the articular
surfaces, except that of this medium position, exhibits
a forced state in which some ligaments are necessarily
more stretched than others, and in which the osseous surfaces
are never in so general contact as in this position.
In certain fevers which have so deleterious an influence
upon the muscular life and texture, the horizontal prostration
and extension of the extremities do not arise from
an increase of the action of the extensors, but from the
want of energy of the flexors, which have not power to
overcome the weight of the limb; thus observe that every
analogous attitude always coincides with the signs of
general weakness; this is the attitude of putrid fevers, &c.
The section of a living muscle presents us with two
phenomena which are evidently the product of the contractility
of texture.
1st. The two ends retract in opposite directions; there
exists between these divided ends a space proportional to
the retraction. This retraction is not in proportion, as
has been thought, to the degrees of the contractions of
the muscle; if it was, it would be sufficient in a transverse
wound, in order to bring the divided edges together,
to place the limb in the greatest possible relaxation;
now oftentimes, in these cases, these ends still remain
at a distance; then the retraction is often superior
to the greatest contraction of the muscle considered in
its natural state.
2d. The antagonist of the divided muscle which has
no effort to overcome, contracts and makes the moveable
part incline from its side, if there are not other muscles,
which acting in the direction of the first supply its functions.
This last phenomenon takes place also to a certain
extent in paralysis of the face. The mouth is then drawn
from the sound side. I have observed however in this
respect, that this deviation is never as evident as it
would be by the division of the paralytic muscle, which
has preserved its contractility of texture. This remaining
contractility forms a partial equilibrium with that of
the muscles of the sound side, during the absence of motions;
thus the deviations do not become very evident
until the patients wish to speak, until consequently the
vital forces bring into action the sound muscles, which
the others cannot oppose. The paralysis of the sterno-mastoideus
exhibits for the whole head a phenomenon
analogous to that which the preceding muscles produce
for the mouth. Strabismus also oftentimes arises from
this cause.
In general in all the phenomena, it is necessary to distinguish
that which belongs to the vital forces, from that
which arises from the contractility of texture. The muscles
are antagonists as it respects these forces, as well as
it respects this contractility; now as the contraction
dependant on the nervous influence or irritability, is much
more conspicuous than that arising from the organic texture,
the phenomena of the antagonists are much more
striking in paralysis, when the sound muscles are brought
into action in the first manner. It appears that in many
cases of paralysis, the contractility of texture of the
affected side is also a little altered; but it is never so
completely destroyed, that in the amputation of a paralyzed
limb, there is no muscular retraction. I have made
this experiment upon a dog; the nerves having been cut
ten days before, and the limb having remained immoveable
since that period, the division of the muscles produced
a manifest separation between their edges; and even, in
afterwards cutting for the sake of comparison the limb
that remained sound, I did not find any difference.
It is especially when muscles have been first stretched,
and this stretching has ceased, that the contractility of
texture becomes evident. The puncture in ascites and an
accouchement as it respects the abdominal muscles, the
opening of deep abscesses as it respects those of the trunk,
the extirpation of a tumour situated under any muscle,
&c. show us this property in action in a very striking
manner. There is however an observation to be made on
this point, viz. that if the extension has been of long continuance,
or if it has been frequently repeated, the subsequent
contraction is much less, because the muscular texture
has been weakened by the painful state in which it
has been; hence, 1st, the flaccidity of the abdomen after
repeated pregnancy; 2d, the laxity of the scrotum, after
the puncture of an old hydrocele; 3d, I have seen at
Desault's a man who was operated upon in Germany for
a fungus in the mouth, and who had, on that side on
which the disease had been, remarkable wrinkles, owing
to the greater extent of the fleshy part of that side, which
could no longer contract like the other; mastication, at
this time could only be performed on the sound side;
4th, when women have had many children, the diaphragm
is weakened by repeated pressure, and hence in part the
greater mobility of the ribs, which compensate in some
measure in females for the deficiency of action of this
muscle. I think that in many chronic affections of the
chest and abdomen, in which there is a long continued
distension of this muscle, physicians ought more than
they do, to have regard to this cause of difficulty of respiration,
when the principle of distension no longer exists,
as after the evacuation of dropsies, &c.
The extent of the contractility of texture is in the
muscles in proportion to the length of the fibres; hence
why in amputations, the superficial part retracts more
than the deep-seated; why in sleep the phenomena of
contractility of texture are very apparent in the extremities,
the muscles of which are very long; why, in the
antagonists, nature has in general opposed muscles of proportional
length; why consequently, a muscle with long
fibres has rarely for a counterpoise one with short ones,
and vice versa. The flexors and extensors of the arm,
the fore-arm, the thigh and the leg are nearly of the same
extent; the rotators of the humerus within and without,
the first inserted into the sub-spinal depression, the others
into the sub-scapular, resemble each other also in this
respect. The proportion between the antagonists is still
more remarkable on the face, where the same muscles act
most commonly in an opposite direction on each side of
the median line.
The quickness of the contractions, arising from the
contractility of texture, is not like that produced by the
animal or sensible organic contractility, which is uniformly
more or less marked, according as the nervous
influence of the stimulant acts more or less strongly.
Every motion originating from the contractility of texture
is slow, uniform and regular; it is only when the muscular
texture is weakened that it diminishes; it does not
increase except when this texture is more developed;
hence it follows that the varieties of quickness can only
be observed in different individuals, or in the same individual
at different periods, and not, as in the exercise of
the vital forces, from one instant to another. This is a
great and remarkable difference between the two species
of properties.
Death weakens the contractility of texture but does not
annihilate it; a muscle being cut retracts a long time
after life has left it. Putrefaction alone puts a limit to
the existence of this property. It is the same with regard
to extensibility. I would observe however that while
the muscles retain the vital heat, they have more power
of retraction, than when the chill of death has seized them.
Haller places on the same line and derives from the
same principles, the phenomena resulting from the contractility
of texture, which, with some slight differences,
answers to his dead power, and those produced by the
action of the concentrated acids, alkohol, fire, &c. on animal
substances, which crisp, contract and acquire the
horny hardness from the effect of these different agents.
But there are many differences which essentially separate
these phenomena from each other. 1st. The contractility
of texture is very slight in the organs in which the faculty
of having the horny hardness is very evident, for example,
in all the organs of the fibrous, fibro-cartilaginous,
serous systems, &c. &c. 2d. The contractility of texture
is distributed in very various degrees, to the different
parts; from the muscles and the skin, which possess the
greatest degree of it, to the cartilages which seem destitute
of it, there are many variations; on the contrary,
the faculty of acquiring the horny hardness from the
agents pointed out is almost uniformly distributed, or at
least its differences are much less evident. 3d. One becomes
nothing in dried organs, the other is evidently
preserved for many years, as parchment is a proof. 4th.
The first clearly receives an increase of power from life,
especially in the muscles; the second appears to be hardly
modified by it. 5th. This always exhibits sudden effects,
rapid contractions. To feel the contact of the fire, of the
concentrated acids or alkohol, and to assume the horny
hardness, are two phenomena which the second brings
together in the animal parts; the contractility of texture,
on the contrary, exerts itself but slowly, as we have said.
6th. This last can never give to the parts, the muscles
especially, that remarkable density which they exhibit in
their horny hardening. 7th. The absence of extension of
the fibres is the only thing necessary for the contractility
of texture which has an unceasing tendency to activity;
it requires on the contrary in order to crisp the fibres,
that they should be in contact with a foreign body. I
could add to these many proofs, in order to establish an
essential difference between the phenomena confounded
by the illustrious physiologist of Switzerland.
The most of these properties perform a very important
part in the muscles. We shall first examine those of animal
life, and afterwards treat of those of organic.
Properties of Animal Life. Sensibility.
Animal sensibility is that of all the vital properties
which is the most obscure in these organs, at least if we
consider them in the ordinary state. Cut transversely in
amputations, in experiments upon living animals, they do
not experience any very painful sensation; it is only
when a nervous filament is touched, that pain is manifested.
The peculiar texture of the muscle is but slightly
sensible; irritation by chemical stimulants does not show
much sensibility in it.
There is however a peculiar sensation, which in the
muscles very evidently belongs to this property; it is
that which is experienced after repeated contractions, and
is called lassitude. After long standing, it is in the thick
bundle of lumbar muscles that this sensation is especially
felt. After walking, running, &c. if on a horizontal plain,
it is all the muscles of the lower extremities which are
more particularly fatigued; if on an ascending plain, it is
especially the flexors of the ilio-femoral articulation; if
on a descending one, it is the posterior muscles of the
trunk. In the employments which exercise particularly
the superior extremities, this sensation is often experienced
in a remarkable manner, which is certainly not
owing to the compression made by the muscles in contraction,
upon the small nerves which run through them.
In fact it can take place without this antecedent contraction,
as is observed in the commencement of many diseases,
in which it extends in general over the whole muscular
system, and in which the patients are, as they say,
fatigued and wearied, as after a long march. This sensation
appears to depend on the peculiar kind of animal
sensibility of the muscles, a sensibility which the other
agents do not develop, and which the permanency of contraction
renders here very apparent. Thus the fibrous
system, sensible only to the means of distension which
act upon it, does not receive a painful influence from the
other agents of irritation. Observe that this painful sensation,
which a too prolonged motion produces in the
muscles, is intended by nature to warn the animal to
place limits to it, without which the consequences would
be serious. Thus the peculiar sensation which arises
from distended ligaments, is designed to make the animal
limit their extension. Observe how each organ has its
peculiar kind of sensibility; how false an idea we should
have of the existence of this property, if we judged of it
only from mechanical and chemical agents, and observe
particularly how nature accommodates to the uses of each
organ its kind of animal sensibility.
In phlegmasia of the peculiar muscular texture, the
animal sensibility is very often raised to a very great
height; the least touch on the skin becomes painful; the
patient can hardly bear the weight of the clothes, and
frequently the least jar produces in the limbs the most
acute pains. But in general these pains are wholly different
from the painful sensation which we call lassitude;
thus the pain of a ligament stretched in a sound state, is
not the same as that which arises from the inflammation
of a ligament or any other fibrous organ.
I would add to what I have said above upon this sensation,
that some organs are fatigued like the muscles, from
too long continuance of their functions; for example, the
eyes by the contact of light, the ears by that of sounds,
the brain by thinking, &c. and in general all the organs
of animal life; it is even this general lassitude which
brings on sleep, as I have proved in my Researches upon
Life. But observe that the sensation which the eye, the
ear, the brain and all the external organs produce when
thus fatigued is not the same as that which arises from the
over-exertion of the muscles; another proof of the peculiar
kind of their sensibility, and in general of that of every
living part.
Animal Contractility.
This animal property, upon which all the phenomena
of locomotion and voice depend, which assists those of
the internal and external functions, has its seat exclusively
in the animal muscular system; it is this which distinguishes
it from the organic, and from all the others.
It consists in the faculty of moving under the cerebral
influence, whether the will or other causes produce this
influence. The animal contractility has then, like the sensibility
of the same species, a peculiar character, differing
from the two organic contractilities, a character which
consists in this, that its exercise is not concentrated in the
organ which is moved, but that it requires also the action
of the brain and the nerves. The brain is the principle
from which, if we may so say, this property goes, as it is
that to which all the sensations come; the cerebral nerves
are the agents which transmit it, as they are, though in
an opposite direction, the conductors of the sensitive phenomena.
Whence it follows, that in order to understand
this property well, it is necessary to examine it in
the brain, in the nerves and in the muscle itself.
Animal Contractility considered in the Brain.
Every thing in the phenomena of animal contractility
proclaims the influence of the brain.
In the ordinary state if more blood is carried to this
organ, as in anger; if opium, taken in a moderate dose,
excites it slightly; if wine produces the same effect, the
muscular action increases in energy in proportion as that
of the brain is thus increased. If terror by retarding the
pulse, by diminishing the force of the heart, and even the
quantity of blood sent to the brain, strikes it with atony;
if the different narcotics, carried to excess, produce the
same effect; if wine prevents its action by its too great
quantity, then observe these muscles languish in their
motion and experience even a remarkable intermission.
If the brain is wholly engrossed in its relations with the
senses, or in its intellectual functions, it, if we may so
say, forgets the muscles; these remain inactive; the
man who looks or hears with attention, does not move;
neither does he who contemplates, meditates and reflects.
The phenomena of ecstasy, the history of the studies of
philosophers, often present us with this important fact,
this muscular inertia, the principle of which is in the distraction
of the cerebral influence, which does not increase
in other functions, only by diminishing in locomotion.
In diseases, all the causes which act strongly on the
brain, re-act suddenly on the animal muscular system;
now this reaction is manifested by two opposite states,
by paralysis and by convulsions. The first is the indication
of diminished energy, the second that of increased;
one takes place in compressions from pus, effused blood,
bones driven below their natural level, and from the consequences
of apoplexy; it is seen in the attack of most
hemiplegias, a sudden attack in which the patient falls
down, loses all consciousness and has all the signs of a
cerebral lesion. This lesion disappears, but its effect
remains, and this effect is the immobility of a part of the
muscular system. The other state or the convulsive,
arises from the various irritations of the cerebral organ
from osseous fragments driven into its substance, from its
own inflammation or that of its membranes, from different
tumours of which it may be the seat, from organic lesions
that it may have, lesions which I have rarely observed in
the adult, but which infancy sometimes exhibits, and
from the causes even of compressions; for oftentimes we
see this convulsive state existing at the same time with
different effusions, with hydrocephalus, &c.
The state of the animal muscular system is truly the
thermometer of the state of the brain; the degree of its
movements indicates the degree of energy of this organ.
Those who attend in a lunatic hospital have often occasion
to consult this thermometer. At the side of a
furious patient, whose muscular power is doubled, or
even trebled, you see a man all whose motions languish
in a remarkable inertia. A thousand different degrees
are observed in these motions; now these degrees
do not depend upon the muscles; the most furious madman
is often he whose very delicate external forms indicate
the weakest muscular constitution; as the most perfect
automaton is sometimes he whose muscles are the
most powerfully developed. The muscles are to the brain
what the arteries are to the heart. The physician learns
by these vessels the state of the central organ of circulation
which communicates impulse to them; by the
muscles of animal life, he learns the state of the central
organ of this life. Observe patients in many important
fevers; in the morning there is prostration, in the evening
you find an extreme agitation in the muscles. Now
what is the seat of this revolution? It is not the muscles,
but it is the brain. There has been a translation to the
head, as it is commonly called.
If from the bed of the sick we go to the laboratory of
the physiologist, we shall see experiments in perfect
accordance with the preceding observations. The ligature
of all the arteries that go to the brain, interrupts
immediately the movements of this organ, movements
necessary to its action, and produces a sudden cessation
of voluntary motion, and afterwards death. By injecting
through the carotid and towards the head, ink, solutions
of neutral salts, acids, substances whose contact is fatal to
cerebral action, I have always seen the animal perish with
previous convulsive motions. The injection of water
does not produce this effect; it can with impunity to the
life of the brain be introduced into the arterial blood, if
it is injected moderately; but pushed with force, you
will irritate extremely this organ, and in an instant the
animal is seized with violent agitations; moderate the
force, rest succeeds. I have already related this experiment
elsewhere. If we lay bare the cephalic mass, and
irritate it with a mechanical or chemical agent, &c. in an
instant the animal muscular system is brought into action.
It is however to be observed that in these experiments
the convexity of the organ appears to be much less connected
with the motions, than its base. The irritation
confined to the cortical substance, to the superficial layers
of the medullary, is almost nothing; it is not till we
arrive at the inferior layers, that the convulsions come
on. I have wished to try many times to ascertain with
precision the place where the irritation becomes a cause
of convulsion; but this has always appeared to me very
difficult, and the results have been infinitely various. I
believe that we can hardly establish any thing more than
a general result, viz. that the nearer we approach in the
experiments the annular protuberance, and in general the
cerebral base, the more apparent are the convulsive phenomena;
they are so much the less as we remove from
them, they are nothing on the convex surface. Observe
that it is on the side of its base, that is to say, on the side
of its essential part, that the brain receives the numerous
vessels which carry to it excitement and life, whether
by the motion which they communicate to it, or by the
nature of the red blood which they carry to it, as my experiments
published the year passed have, I think, demonstrated.
Add to these experiments those of the artificial commotions.
The muscles of the ox vacillate, and are unable
to support themselves, the instant the blow is struck.
At other times animals expire, their limbs convulsively
agitated from a blow given on the occiput; rabbits often
exhibit this phenomenon. Pigeons die with convulsive
motions of the wings. Irregular agitations arising from
an irregular influx of the power of the brain always precede
the instant of death, which the commotion has produced.
Let us conclude from all these experiments and the
observations that precede them, that the action of the
animal muscular system is always essentially connected
with the state of the brain, and that when this action is
increased or diminished there is almost always an increase
or diminution of the cerebral action.
Let us not however exaggerate the relation which connects
the muscular to the cerebral phenomena; observation
would prove us incorrect. There are various examples
of aqueous, sanguineous and even purulent congestions
in the brain, without having produced any alteration
in muscular motion. Different tumours and defects
of conformation have occasioned disturbance of the intellectual
functions, without affecting those of the muscles;
how many times is the brain disordered in various species
of alienations; how many times do the understanding,
memory, attention and imagination indicate these derangements
by their irregular aberrations, without their being
felt by the muscular system. Is there not often an alteration
of the external sensation, without an alteration of
motion? In general the brain has three great functions.
1st. It receives the impressions from the external senses;
it is in this relation the seat of perception. 2d. It is the
principle and the centre of the voluntary motions, which
are not exerted but by its influence. 3d. The intellectual
phenomena are essentially connected with the regularity
of its life; it is as it were the seat of them. Now
it can be deranged as to one of these functions, and remain
sound as to the others; it can be a regular principle
of the motions, and an irregular centre of the phenomena
of the understanding; not communicating with external
objects by the senses, and determining motions, or presiding
over intellectual functions, as happens in sleep
which is disturbed by dreams, &c.
From what has been said we can understand why acephalous
fœtuses cannot live out of the womb of the
mother. As animal life is nothing in the fœtus, as respiration
does not take place, as the functions are limited to
the great circulation, to the secretions, exhalations and
nutrition, the acephalous fœtuses can live in the womb
of the mother, and acquire a very considerable size;
but at birth they cannot breathe, the intercostals and diaphragm
being unable to act. The gastric viscera receives
no influence from their muscular parietes; all the
limbs are immoveable. Animal life, which commences in
others at birth, cannot commence in them, because they
have not the centre of this life; they have senses, but
nothing to receive their impressions; muscles, but nothing
to make them move; they can continue to live but a little
while in themselves, without beginning to live from
without. But as in general it appears that when the infant
quits the womb, the red blood becomes necessary to
it, that to have this, it must respire, and as this function
cannot commence, it loses the internal life which it had
in the womb of the mother. There are acephalous fœtuses
which have at the origin of the nerves a small medullary
swelling; in others the spinal marrow is larger. If these
medullary swellings, if the spinal marrow by its peculiar
texture, supply the place of the brain, life can continue,
and it is in this way that we can explain some examples
of acephalous subjects that have lived a certain time. But
certainly an acephalous subject organized like ourselves,
which has nothing to supply the place of the brain, cannot
live. Thus in almost all the examples of these monsters,
related by authors, and especially by Haller, the
death of the individual took place at its birth.
Animal Contractility considered in the Nerves.
The brain, at a distance from almost all the muscles,
communicates with them by the nervous system, and by
it transmits to them its influence; now this communication
is made in two ways. 1st. There are nerves which
go directly from the brain to the muscles of animal life.
2d. The greatest number does not go from this organ
itself, but from the spinal marrow. Almost all the muscles
of the neck, all those of the chest, the abdomen and
the extremities receive theirs from this last source. The
spinal marrow is, as it were, a general nerve, of which
the others are only divisions and principal branches.
All the lesions of this principal nerve are felt by the
muscles that it has under its influence; the compressions
that it experiences from a fracture of the vertebræ, from
any displacement, from an effusion of blood, serum, pus,
&c. in the vertebral canal, the derangements which take
place from a violent blow received upon the whole region
of the spine, from a fall upon the loins, or on the superior
part of the sacrum, are followed by numbness and paralysis
of the subjacent muscles. Divide the spinal marrow,
by introducing a scalpel into the canal, immediately all
motion ceases below the division. If you wish on the
contrary to produce convulsions, introduce a stilet into
the canal; irritate the marrow with it or by chemical
agents placed on it, there will be immediately agitation
and convulsion in all the animal and muscular system
that is below.
The higher the lesion of the marrow is, the more dangerous
is it. In the lumbar region its influence extends
only to the inferior extremities, and the muscles of the
pelvis; in the back it paralyzes these muscles and those
of the abdomen; now as these last contribute indirectly
to respiration, this function begins to be embarrassed; if
the lesion is above the dorsal region, it becomes still more
painful, because the intercostals lose their action; the
diaphragm alone then supports the respiratory phenomena,
because the phrenic nerve still receives and transmits the
cerebral influence. But when the lesion happens above
the origin of this nerve, there is no more action of the
diaphragm, and no more contraction of the intercostal and
abdominal muscles; respiration ceases; from the same
cause the circulation is interrupted; the blood being no
longer carried to the brain, the action of this organ is annihilated.
Hence why the luxations of the first vertebra
on the second are suddenly fatal, when the displacement
is very great; why judicious surgeons dare not sometimes
run the hazard of reduction, when these luxations are
partial, for fear of rendering them complete, and of thus
seeing the patient, whom they attempted to relieve, perish
in their hands; why, when we wish to knock down an
animal, the blow should be given on the superior and
posterior part of the spine; and why a stilet plunged between
the first and second vertebræ immediately destroys
life.
We see very distinctly the successive influence of the
different parts of the marrow on the muscles and on the
general life, by introducing a long piece of iron into the
inferior part of the vertebral canal of an animal, of a
guinea pig for example, and carrying it up through this
canal to the cranium, through the spinal marrow which
it tears. We observe evidently as it ascends, at first
convulsions of the inferior extremities, then those of the
abdominal muscles, then derangement of respiration,
then its cessation, then death which is the consequence
of it.
From all these facts, we cannot, I think, call in question
the influence of the spinal marrow upon motion, the
principle of which it receives from the brain and afterwards
transmits it to the nerves. These last carry this
principle, which they have received, to the muscles, either
by means of the spinal marrow, as in almost all those of
the trunk and the extremities, or directly from the brain,
as in those of the face, the tongue, the eyes, &c. There
are the same proofs for this nervous influence, as for that
of the preceding sensitive organs. The tying, division
or compression of a nerve paralyzes the corresponding
muscle. Irritate with any agent a nerve laid bare in an
animal, convulsive contractions are immediately seen in
the muscle. These experiments have been so often and
so accurately repeated by many authors, that I think it
useless to go into details, which the reader may find
everywhere. Irritation continued some time upon one
point of the nerve destroys its influence upon the muscle,
which remains immoveable; but it is put in motion again,
if the irritation is carried to a lower part of the nerve.
If we tie it, the motion ceases, if irritation is made above
the ligature, it returns when it is made below, or when
the ligature is removed.
I would remark that all the nerves of animal life do
not appear to be equally capable of transmitting to the
muscles the different irradiations of the brain. In fact
whilst in diseases, in wounds of the head, in our experiments,
&c. the muscles of the extremities are convulsed or
paralyzed with great ease, those of the abdomen, the neck,
and especially the chest do not exhibit these phenomena,
except when the causes of excitement and debility are
carried to the highest point. Nothing is more frequent
than to see the abdomen and the chest with their ordinary
degree of muscular contraction, whilst the extremities or
the face are agitated with convulsive motions. Examine
most hemiplegias; the mouth is twisted, the superior and
inferior extremity of one side become immoveable, and
yet the pectoral and abdominal motions continue. Those
of the larynx are more easily interrupted than these in
paralysis; hence the different injuries of the voice. We
could make a scale of the susceptibility of the muscles to
receive the cerebral influence, or of the nerves to propagate
it, for it is difficult to determine to which of these
two causes the phenomenon is owing; we could, I say,
make a scale, at the top of which should be placed the
muscles of the extremities, then those of the face, then
those of the larynx, afterwards those of the pelvis and
the abdomen, and finally the intercostals and diaphragm.
These last become convulsed and paralyzed with the most
difficulty of all. Observe how this scale is adapted to that
of the functions. What would become of life, which is
always actually connected with the soundness of respiration,
if all the cerebral lesions were as easily felt by the
diaphragm and the intercostals, as by the muscles of the
extremities? Paralysis in these last only takes from the
animal a means of communication with external objects;
in the others it interrupts immediately both internal and
external life.
The nervous influence is only propagated from the
superior to the inferior part, and never in an inverse
direction. Cut a nerve in two, its inferior part when
irritated will make the subjacent muscles contract; let
them do what they will to excite the other, no contraction
is produced in the superior muscles; so the spinal marrow
divided transversely and pricked above and below, produces
no sensible effect but in the second direction. The
nervous influence never extends upward for motion, as it
does for sensation.
Animal Contractility considered in the Muscles.
The muscles essentially destined to receive the cerebral
influence by means of the nerves, have however an active
part in their own contraction. It is necessary that they
should be entire to exercise this property, and answer to
the excitement of the brain. When any lesion affects
their texture, and it is no longer the same as usual, the
muscle remains immoveable or moves with irregularity,
though it receives a regular nervous influx. The following
are various circumstances relative to the muscle itself,
which prevent or alter its contractions.
1st. An inflamed muscle does not contract; the blood
which then infiltrates it and penetrates its fibres, their
great excitement and the increase of its organic forces, do
not permit it to obey the stimulus it receives. In angina,
deglutition is as much interrupted by the inaction of the
muscles, as by the inflammation of the mucous membrane.
We know that the inflammation of the bladder is one
cause of the retention of urine; that of the diaphragm
renders respiration very painful, which the intercostals
perform almost alone.
2d. Every thing which tends to weaken and relax the
muscular texture, as external blows, bruises, contusions,
infiltrations of serum in dropsical limbs, or distension
from a subjacent tumour long continued, alters, changes
the nature of, and can even annihilate animal contractility.
3d. Whenever the blood ceases to enter the muscles by
the arteries, these organs remain immoveable. Steno has
observed, and I have always seen, that in tying the aorta
above its bifurcation which forms the internal iliacs, paralysis
of the inferior extremities immediately comes on.
We know that in the operation for aneurism, a numbness
more or less considerable almost always follows the ligature
of the artery. This numbness continues until the
anastomoses supply the place of the artery which no
longer brings any fluid. The internal motion created in
the muscle by the entrance of the blood, is then a condition
essential to muscular contraction. Thus the habitual
motion imparted to all the other organs and especially
to the brain, maintains their excitement and their life.
4th. It is necessary in order to obey the cerebral influence
that the muscle should not only receive the shock of
the blood, but also of the red or arterial blood. Black
blood cannot by its contact support motion. A general
weakness and the fall of the animal are the first symptoms
of asphyxia, a disease in which the black blood goes to
all the parts. I shall not here repeat the proofs of this
assertion, which appears to me to be amply demonstrated
by my Researches upon the Different Species of Death.
I refer to my work upon this point.
5th. A fluid differing from the blood, water, oily and
albuminous fluids, and for a stronger reason acrid and irritating
fluids, the urine, solutions of the acids and the
alkalis, &c. are not proper to support muscular action;
on the contrary they paralyze it; injected into the crural
arteries of a living animal instead of blood, which is stopt
above by a ligature, they weaken and even annihilate the
motions, as I have frequently satisfied myself. The result
varies in these experiments according to the fluid employed
in making them; the rapidity of the cessation of
the motions is more or less striking; they are either
weakened or totally suspended; but there is always a
very great difference between that and the natural state.
6th. Does the contact of the different gases upon the
muscles modify their contractions? Since the publication
of my Treatise upon the Membranes, I have made
no experiment upon this point. Those which are contained
in it present the following results; frogs and
guinea pigs rendered emphysematous by blowing air into
the sub-cutaneous texture which afterwards penetrates the
cellular interstices, and comes everywhere in contact
with the muscular system, move almost the same as usual.
If oxygen is used, the motions of the emphysematous
animals are not accelerated; they are not diminished if
we employ the carbonic acid gas, hydrogen, &c. In general,
all the artificial emphysemas that I have made upon
the two species mentioned, in order to have an example
in each class of animals with red and cold blood, and of
those with red and warm blood, succeeded very well, and
did not appear to cause any sensible embarrassment to the
animal, which gradually got rid of it. Emphysema with
nitrous gas is constantly fatal; the contact of this gas
seems almost suddenly to strike the muscles with atony.
7th. If instead of blowing gas into the cellular texture
of an animal, we force in different fluid substances, they
produce different effects upon the muscles, according to
their nature, and to their acrid, soft, or styptic qualities.
No injection produces a more sudden and striking effect
than that of opium dissolved in water, or than that of its
various preparations; when the muscles feel it in contact,
their motions cease, they fall as in paralysis.
In general I would observe that it is infinitely better
to make the experiments of the contact of the gases and
the different fluids upon the muscles, by blowing the first,
and injecting the others into the intermuscular texture of
a living animal, than by drawing out a muscle, and afterwards
plunging it all alive into the one or the other; or
than laying a muscle bare, in order to direct upon it the
current of a gas, or to moisten it with a fluid, for the purpose
of observing the phenomena of the contact.
It follows from all that we have just said, 1st, that to
answer to the cerebral excitement by contracting, the
muscle should be in general in a state determined by the
laws of its organization; that out of this state it is not
capable of contracting, or at least that it does it feebly
and irregularly; 2d, that the contact of different foreign
substances produces upon the muscle a very variable
effect. Moreover many causes besides those stated above,
appear to me also to alter the contractions, by acting
directly upon the muscles, such as mercury taken by friction
for the venereal disease, the influence of this metal,
of copper and of lead, upon those who work in them,
the action of cold, that of certain fevers, &c. The muscular
tremor arising from these different causes, does not
appear to arise from the brain; this organ at least does
not most commonly give any sign of affection in this
case; I confess however that in these different species of
tremors, it is not easy to distinguish that which belongs
to the peculiar affection of the muscle, from what arises
from that of the nerves; perhaps these are especially
affected, but the brain certainly does not participate.
Causes which bring into action Animal Contractility.
We have just seen that in the natural state this property
constantly requires three actions, 1st, that of the brain;
2d, that of the nerves; 3d, that of the muscles; that it is
from the brain that the principle of motion goes which is
propagated by the nerves, and which the muscles receive.
But it is necessary that some agent should excite the
brain to determine it to exert its influence. In fact, the
animal contractility being essentially intermittent in its
exercise, so that each time after it has been exerted it is
suspended, it is necessary that a new cause should place
it again in activity; now this cause acts at first upon the
brain in the natural state.
I refer to two classes the causes that excite the brain in
order to produce animal contractility. In the first is the
will, in the second are all the impressions which this organ
receives, and which are not under the control of the
mind.
The brain is only intermediate between the mind and
the nerves, as the nerves are between the muscles and the
brain; the principle, which wills, acts at first upon this
organ, which afterwards re-acts. When they are thus produced,
our motions are sometimes precise and regular;
that is when the intellectual functions are sound, when
the memory, imagination and perception are clearly exerted,
when the judgment being correct, directs with regularity
the acts of the will; sometimes they are irregular
and singular, it is when the intellectual functions disturbed
and agitated in various ways, produce a singular and
irregular volition, as in the various mental alienations, in
dreams, in the delirium of fevers, &c. But in all these
cases, these are always voluntary motions; they go from
the immaterial principle that animates us.
In the second class of causes which influence the brain,
the animal contractility becomes involuntary; it is exerted
without the participation of the intellectual principle,
often even against its will. Observe an animal whose
brain is artificially irritated in experiments; it tries to
stiffen itself to prevent the contractions, they take place
in spite of it; prick a nerve in an operation, the muscle
contracts suddenly below, without the mind's participating
in this movement; the patient has not even a consciousness
of it; he has only that of the pain. When much
blood flows to the brain in the violence of inflammatory
fevers, this organ excited by the fluid, re-acts immediately
upon the muscles, without the will's partaking in it. All
the phenomena of contraction and relaxation, arising from
different accidents which accompany wounds of the head,
cerebral inflammations, &c. are equally involuntary, although
having their seat in the muscles which the will
habitually directs. These are the different circumstances
in which the action of any agent upon the brain is direct
and immediate, and in which there is a mechanical cause
applied to the brain.
In other circumstances the brain is only affected sympathetically.
In many acute affections what is called translation
to the brain, does not arise from more blood being
carried to it; the pulse is not fuller, the face is not more
flushed; there are often even signs of languor in the action
of the vascular system. The brain is affected, like
all the other organs by sympathy, a happy word, which
serves to veil our ignorance in respect to the relations of
organs to each other; the brain is affected then like the
heart, the liver, &c. Take for example peripneumony;
the lungs are then the organs that are essentially injured,
from this essential and local injury, arise many sympathetic
ones more or less severe. If the liver is sympathetically
affected, bilious symptoms are joined to the
symptoms of the principal affection; if it is the stomach
then gastric symptoms are manifested. The heart is always
agitated; hence there is fever. When the sympathetic
influence extends to the brain, there is violent motion,
convulsions, &c.; for, as I have said, the state of
the muscles is the index of the state of this organ; now,
in this last circumstance, the will has nothing to do with
the animal contractility in exercise; the patient cannot
prevent the convulsive agitation of his muscles; the
sympathetic irritation of the brain is stronger than the
influence of the will. This example of cerebral affection
in peripneumony, though more rare than in many other
diseases, may however give us an idea of what takes
place in all other cases in which the muscles are convulsively
agitated by the injury of any organ, by that of
the fibrous system distended, of the ligaments and especially
of the aponeuroses, by dentition, by violent pains in
the kidneys, in the salivary glands or the pancreas, occasioned
by a stone, by injuries of the diaphragm, the nerves,
&c. In all these cases, there is an affected point in the
economy; from this point the sympathetic irradiations
go off, which especially reach the brain; this irritated by
them, enters into action and excites the muscles; their
contraction takes place and the will is a stranger to it.
See also how the passions which have their influence
particularly over the internal organs, which especially affect
those placed around the epigastric centre, the heart,
the liver, the stomach, the spleen, &c. imprint on our
motions an impetuosity, which the will cannot make us
masters of. The internal organ affected re-acts upon the
brain, this excited stimulates the muscles; they contract,
and the will is almost nothing in this contraction. Observe
the man, whom jealousy, hatred or rage agitates to
the greatest degree; all his movements follow each other
with an impetuosity which judgment reproves, but which
the will cannot moderate, so much does the influence of
the sympathetic affection of the brain predominate over
that of the will. At other times the passions exhibit an
opposite phenomenon. They are marked by a general
weakness of all the muscular motions. In astonishment
accompanied with grief, or in that in which is mixed a
lively joy, the arms fall down as it is commonly expressed;
the cerebral influx ceases almost entirely, and yet it
is not to the brain that the influence of this passion is
carried, it is to the epigastric centre, as is proved by the
sudden contraction which is felt there. One of the epigastric
organs has been affected; it has reacted upon the
brain; this has been interrupted in part in its functions;
the muscles feel it and theirs cease. In fear in which
this phenomenon is observed, as the paleness of the skin
indicates the languor of the circulating system, it may
happen that the cerebral and muscular inaction arises in
great measure from this, that there is not received a sufficient
impulse from the heart, upon which the first influence
of the passion is exerted, and which by this influence
is retarded in its motions. Fear, it is said, takes
away the legs, petrifies, &c.; these expressions, borrowed
from vulgar language, indicate the effect of this passion
on the muscles; but this effect is only secondary; the
first influence has been upon the heart, the second upon
the brain; it is not till after the other two that the muscles
are affected. Hence how certain animals remain immoveable
at the sight of that which is about to seize them
for its prey.
It is also to the sympathetic influence of the internal
organs upon the brain, that should be attributed the motions
of the fœtus, motions which the will does not direct;
for the will is but a result of the intellectual phenomena;
now these phenomena are nothing at this period
of life. The internal functions then very active, suppose
a great action in the liver, the heart, the spleen, &c.; now
these organs in that way influence efficaciously the brain,
and this in its turn puts the muscles in motion; so that
the animal contractility is by no means voluntary in the
fœtus; it does not begin to become so until the sensations
have brought into action the phenomena of the understanding;
until then, they must be compared to all those
of which we have spoken above.
From all that has just been said, it will be easily understood,
I hope, how the animal contractility can be or not
subjected to the influence of the will. In both cases, the
series of phenomena which it requires is always the same;
there is always excitement by the brain, transmission by
the nerves, execution by the muscles, or successive inactivity
of these three organs. The difference is only in
the cause which produces the cerebral excitement; now
this cause can be, 1st, the will; 2d, an irritation immediately
applied; 3d, a sympathetic irritation. It is essential
to form precise and exact ideas concerning this vital
force which performs so great a part in the living economy.
Duration of the Animal Contractility after Death.
The difference of the causes which act upon the brain
in the animal contractility, in order to determine it to
excite the muscles, appears particularly in a remarkable
manner at the instant of death. Whatever may be the way
in which this happens, the intellectual functions are always
the first to cease; it is even to this that we especially
attach the idea of the absence of life. Whence it follows
that the first phenomenon of this absence must be the
failure of the muscular contraction subjected to the influence
of the will, which is the result of these intellectual
functions. Every thing then remains immoveable in the
muscular system, if no other cause acts upon the brain
or the nerves; but these two organs are, yet for a long
time, capable of answering to the various excitements of
stimuli. Stimulate in any way the brain, the spinal
marrow or the nerves of an animal recently killed, in
an instant its muscles convulsively contract; it is the
same phenomenon as that obtained during life from the
same cause. Often even immediately after death, this
phenomenon is still more apparent than during life; I
have been frequently convinced of this in my experiments.
If during life we irritate any nerve, the contraction
oftentimes is almost nothing, because the will acting
by the other nerves upon the same muscle, or at least
upon those of the limb, produces contractions opposite to
those which the irritation tends to produce. I have many
times observed that the galvanic phenomena are also infinitely
more easily produced an instant after death, even
in animals with red and warm blood, than during life;
in this last case often we can obtain hardly any result,
because their influence is counteracted by the cerebral
influence arising from the will. When the irritation is
directly applied to the brain or the superior part of the
spine, it then surpasses the will; it is stronger in the
living animal; but on an insulated nerve, it is often inferior
to it; not that the will acts by the irritated nerve,
its influence in it is arrested at the place stimulated, but
it exerts itself by the adjacent nerves.
It is to the susceptibility of the brain and nerves of
still transmitting the principle of motion after death, that
must be referred all the phenomena that are witnessed in
the different kinds of decapitation. Ducks, geese and
other animals of this family move their muscles with
some regularity, after the head is taken off, in running,
jumping, &c. Some time after the punishment of the
guillotine, the inferior and superior extremities are still
the seat of various tremors; the muscles of the face are
sometimes even contracted so as to give to this part the
expression of certain passions, an expression incorrectly
referred to the sensitive principle still left for some time
in the brain. The same phenomena were formerly observed
in the punishment that consisted in cutting off the
head with an axe. During the year past I have had a
painful proof of these singular facts; a guinea-pig, whose
heart I had just removed, plunged deep into my finger
the four prominent teeth that distinguish this species.
All these phenomena are only the result of the irritation
produced, either by the cutting instrument, or by the
air, upon the two divided extremities of the marrow;
this is so true, that by increasing the irritation by a pricking,
cutting instrument, &c. with a chemical agent applied
to these extremities, the motions are very much increased.
Nothing is more easy than to be convinced of this fact
in an animal; I have many times proved it in those who
have been guillotined, upon whom I have been allowed
to make experiments for galvanic purposes. See how
the alternate motions of respiration can continue for some
time, after the brain has been destroyed, after a wound of
the head in which its mass has been crushed, after a luxation
of the first vertebra, in which the beginning of the
spinal marrow has been compressed so as suddenly to
stop life, after the injection of a very irritating fluid by
the carotid, &c. &c.
In this duration of animal contractility after death, the
muscles are absolutely passive; they obey, as during life,
the impulse they receive from the nerves; it is this
which distinguishes it essentially from the duration of
irritability, a property by which, after death as during
life, the muscle has in it the principle which makes it
move.
The duration is greater or less according to the class of
the animals; those with red and cold blood keep this
property longer than those with red and warm blood;
among these, the family of ducks are, as I have said,
remarkable for this phenomenon, which is much more
rapidly lost in the others and in quadrupeds. In the
first class there are also varieties among the reptiles,
fishes, &c.
In general I have constantly observed that the animal
contractility ceases after death, first in the brain, then in
the spinal marrow and last in the nerves. When the
muscles no longer move by irritating the first of these
organs, they contract by stimulating the others. The
irritated nerves can still communicate a motion, when the
spinal marrow, no longer exhibits this phenomenon. I
have not observed that the superior part of the nerve
ceased sooner to transmit motion, than the inferior. But
what is remarkable is that certain nerves, under the influence
of the same irritation, make their muscles contract
more strongly than others; such for example is the
phrenic. When all the other muscles cease to be moveable
by the artificial excitement of their nerves, the diaphragm
is still moved by this means. Whilst experiments
have but little effect elsewhere, they are in full force
upon this muscle; this is the more remarkable, as during
life this is precisely the one which is the least affected
by the state of the brain and the spinal marrow; paralysis
and convulsions hardly ever affect it, as we have seen.
Besides, in thus comparing the duration of animal contractility,
the same stimulant should always be employed;
for the effects are more or less evident according to
those which we use. When the whole brain and the
nerves are no longer sensible to mechanical or chemical
agents, they still powerfully obey galvanic impulses.
The irritation of the metals is of all the means at present
known, the most efficacious in perpetuating animal contractility
some time after death.
Organic Properties.
Organic sensibility is the manifest portion of the muscles
of which we are treating; constantly brought into
action in them by nutrition, absorption and exhalation, it
becomes still more apparent, when we irritate muscles
that are laid bare; they feel this irritation, and the motion,
of which we shall speak hereafter, is the result of
this feeling which is centred in the muscle, and which is
not referable to the brain.
Insensible organic contractility is the attribute of this
muscular system, as of all the others.
The sensible organic contractility is very evident in it.
If we lay bare a muscle in a living animal, and irritate it
with any agent, it curls up, contracts and is agitated. A
detached muscular portion exhibits for some instants the
same phenomenon.
Every thing is irritating to the naked muscle, the air,
water, neutral salts, the acids, the alkalis, the earths,
metals, animal and vegetable substances, &c. The mere
contact is sufficient to produce contraction. Yet besides
this contact, there is something also which depends upon
the nature of the stimuli, and which makes the intensity
of the contractions vary. A powder of wood, coal,
metal, &c. sprinkled upon the muscles of a frog, produce
but slight motions in it; pour on it a neutral salt in powder,
the marine salt for example, immediately irregular
agitations, and a thousand different oscillations are manifested.
Each body is by its nature capable of irritating
the muscles differently, as according to individuals, ages,
temperaments, seasons, climates, &c. the muscles are
capable of answering differently to excitements made
upon them.
It is not necessary to irritate the whole of a muscle to
produce its contraction; two or three fibres only being
pricked bring into action all the others. Often even when
we make these experiments on a living animal, the contraction
is communicated from one muscle to another.
In general I have constantly observed that during life
these experiments are less easy, and give results much
more various, as we have already stated with regard
to animal contractility. Lay bare a muscle, irritate
it at many different times; sometimes it does not give
the least sign of contractility; sometimes it moves with
force; this varies from one instant to another. Whereas
if it is upon an animal recently killed that the experiments
are made, the results are always nearly the same
in a given time, with the difference however of the weakness
which the contractions have in proportion to the
length of time after death. It never happens that you
see a muscle immoveable under stimuli, which is not rare
in a living animal. This essential difference which authors
have not sufficiently pointed out, and which I have
frequently proved upon different animals, arises from this,
that during life, the effects of the nervous influence counteract
those of the stimuli; for example, if an animal extends
with force his thigh by the posterior muscles, we
may in vain irritate the anterior ones, we cannot produce
flexion by this irritation. The cerebral excitement in
the extensors being stronger than the mechanical excitement
in the flexors, triumphs. Often when we apply
the stimulant, the brain acts with force upon the muscle,
the effect is then much superior to the excitement we
have applied. We are astonished; but the astonishment
ceases, if we recollect that there is a concurrence of two
excitements, of that of the external agent and of that of
the brain. In general, those who have made experiments,
have not paid sufficient attention to this concurrence of
the two forces in a living animal.
In order to estimate correctly the sensible organic contractility,
it is necessary to destroy the animal contractility.
So long as these two clash, interrupt and counterbalance
each other, we cannot properly estimate them,
and determine what belongs to each and what is common
to both. Now we destroy animal contractility in the
living subject, by cutting all the nerves of a muscle or an
extremity, which then become paralyzed. The brain
can no longer act upon them, and the results we obtain
from stimuli, belong to the sensible organic contractility.
The duration of this last property, after the experiment
I mentioned, proves completely that the nerves are
wholly foreign to it, that it resides essentially in the
muscular texture, that it is, as Haller said, inherent in it.
Thus whilst in the different paralyses the muscles lose
the power of obeying the cerebral influence, or rather
this influence becomes nothing, they preserve that of
contracting in an evident manner when stimulated.
This contraction of the muscles of animal life by stimulants,
appears under two very different modes. 1st. The
whole of the muscle can contract and shorten so as to approximate
the two points of insertion. This happens in
general when death is recent, when the muscle is still fully
possessed of life. 2d. There are oftentimes numerous
oscillations of the fibres; all are in action at the same
time; now this action is not a contraction, but a real
vibration, a fluttering, which has not a sensible effect upon
the whole of the muscle, which not contracting cannot
approximate its moveable points. When life is about
abandoning entirely the muscle, it is thus that it moves.
The diversity of the stimuli occasions also this double
mode of contraction. Carry a scalpel over a living muscle,
a contraction of the whole will be the consequence;
afterwards sprinkle the same muscle with a neutral salt,
sometimes there is an analogous contraction; but frequently
there are only oscillations, vibrations similar to
those of a muscle which life abandons.
During the life of the animal, its sensible organic contractility
is rarely in action, because the muscles have not
agents that act upon them in a sensible manner at least.
Why then is this property so developed in them? I cannot
determine.
All the muscles do not possess it to the same degree;
the diaphragm and the intercostals are the most irritable;
they are also those whose organic contractility is the most
permanent after death. Observe that this contrasts, like
their susceptibility to receive the nervous influence by
the irritation of their nerves, especially of the phrenic,
with the little disposition they have to feel, during life,
convulsions or paralysis. After them I think that the
temporal, the masseter, the buccinator, &c. are the most
irritable. There is certainly as it respects irritability a
great difference between them and the muscles of the extremities,
which are all nearly equally susceptible to the
effect of stimulants. Besides, it is only by a great number
of experiments that we can establish general data;
for nothing is more frequent than to find inequalities
between two analogous muscles, and even between the corresponding
ones of the two sides of the body.
Sympathies.
The animal muscular system performs a very important
part in the sympathies. We see it very frequently agitated
with irregular motions in the different affections of
our organs, especially in infancy when every lively impression
made upon any organ, is almost always followed
by spasmodic and convulsive motions in the muscles of
animal life. Observe in fact that it is the vital property
predominant in this system, that is to say the animal contractility,
that is most often brought sympathetically into
action in it, by the influences that the organs exert upon
each other.
In general it appears that when the animal sensibility
is strongly developed in an organ, this system tends immediately
to contract. The acute pains that stones occasion
in the kidneys, in the ureter and even the urethra,
distensions of the ligaments, of the aponeuroses, dentition,
surgical operations in which the patient has suffered
much, &c. produce very numerous and frequent sympathetic
convulsions. I know that there are very severe
pains without sympathetic convulsive motions; but it is
very rare that you see convulsive motions of this nature,
without the organ, from which these sympathetic irradiations
go, is very powerfully affected, and the seat of great
animal sensibility.
Observe on the contrary that most of the sympathies
which develop to a great degree in any part, insensible
organic contractility, or sensible organic contractility, are
not marked by these acute pains in the affected organ
from which the excitement goes; for example, sweats,
sympathetic secretions, intestinal and gastric contractions
are rarely produced by affections of the character of those
from which arise the sympathies of animal contractility.
The brain is always first affected in this last species of
sympathies in which the muscles are, as it were, passive,
as we have already seen, and in which they are made to
obey the impulse they receive. The affected organ acts
at first upon the brain, then this re-acts upon the muscles.
Authors have considered sympathies in too loose a
manner. Some have admitted, others have rejected the
intermediate office of the brain; some have not pronounced
upon it. All would be agreed, if instead of attempting
to resolve the question in a general manner, they had
distinguished the sympathies according to the vital forces,
of which they are only aberrations and irregular developments;
they would have seen, that in the animal sympathies
of contractility, the cerebral action is essential; for we cannot
conceive of any contractility of this species, without
the double influence, nervous and cerebral, upon the muscles;
that on the contrary, in the organic sympathies of
contractility, the action of the brain is nothing; the affected
organ acts directly and without any thing intermediate
upon that which contracts sympathetically. When
the heart, the stomach, the intestines, &c. move, when
the parotid and other glands increase their action by
the sympathetic influence of an affected organ, certainly
this organ does not act first upon the brain; for it would
then be necessary that this should re-act upon those
that contract; now it would not be able to influence them
except by the nerves, since it is only by these that it is
united to them; but all experiments and all facts prove as
we shall see, that the brain has not by this means any influence
over the organs with involuntary motions; then
the action is direct and there is nothing intermediate.
There are sympathetic motions like the natural ones;
the sensible and insensible contractilities are constantly
brought into action by a direct stimulus applied to the
organ, whilst that the animal contractility is never exercised
but by the cerebral stimulant, which itself requires
a cause, either sympathetic or direct, in order to act upon
the muscles.
Next to animal contractility, the sensibility of the same
nature is the most often brought sympathetically into
action in the animal muscular system. The lassitude,
wandering pains, sensation of weight and stretchings that
are felt in the limbs in the beginning of many diseases,
are phenomena purely sympathetic, in which this property
enters into action in the muscles. At advanced periods
of many other affections, these sympathetic troubles are
also very remarkable, but less in general than at the beginning.
The organic properties are for the most part rarely
sympathetically in action in the species of muscles of
which we are treating. Besides, if they are so, we can
hardly judge of it, because no sign points it out to us.
The sweat in the skin, the secreted fluids in the glands,
the fluids exhaled upon many of the surfaces, are general
results which indicate to us the sympathetic derangements
of the organic sensibility and of the insensible contractility
of the same species. In the muscles, we have not
the same means of knowing these alterations.
Characters of the Vital Properties.
From what we have thus far said, upon the muscular
properties and sympathies, it is easily seen that the vital
activity must be in general much greater in the muscles
than in the organs previously examined in this
volume; thus all their affections begin to take a peculiar
character that distinguishes them from those of these organs;
they are much more prompt and rapid. Yet let
us remark that all the alterations of function which they
exhibit, cannot assist us in estimating this vital activity.
In fact, many of these alterations do not reside essentially
in the muscular texture, their cause is not there; such
are for example all the convulsive motions in which, as
we have seen, the muscles act by obeying, but have not
the principle of action in them. They are then the
indices of cerebral alterations; thus the arteries, which
exhibit such numerous varieties in the state of the pulse,
are as it were only passive, and serve most frequently
merely to indicate the state of the heart by their motion,
whilst the veins, which have not at the origin of their
circulation an analogous agent of impulse, very rarely exhibit
varieties, though however their texture may have as
great vital forces, and its life be as active or more so,
than that of the arteries.
One proof that the texture of the muscle is less often
altered than it at first seems to be in considering the frequency
of the affections of these organs, is the infrequency
of their organic lesions. These lesions are even less common
in them than in the bones. We do not see in them
those schirri, swellings, changes of texture in a word,
which are so commonly met with in the other organs.
Among the great number of subjects that I have had occasion
to dissect or to have dissected, I do not recollect to
have seen in the muscles of animal life other alterations
than those of their cohesion, their density and their colour.
It is a phenomenon that approximates them to those of
organic life, in which we rarely meet with changes of
texture, as the heart, the stomach, &c. are examples.
The muscular texture of animal life rarely suppurates;
thus but little is known of its mode of suppuration. In
general, it appears that inflammation terminates in it almost
always by resolution. Induration, gangrene and suppuration,
three terminations that this affection often makes in
the other parts, are unknown to this in the greatest number
of cases.
Thus far we have spoken of muscular mobility, abstractedly
from the phenomena that it exhibits in the
muscles, when it is in exercise in them. These phenomena
are now to be considered. They relate especially
to contraction, which is the essentially active state of the
muscle, relaxation being a state purely passive. We shall
easily understand the phenomena of this, when those of
the other of which they are the reverse are known to us.
The force of the contraction of the muscles of animal
life varies much, according as it is brought into action by
stimulants, or by the cerebral action.
Every irritation made upon a muscle laid bare produces
only a brisk, rapid motion, but generally not very
powerful. I have frequently satisfied myself in my experiments
that it is impossible to approximate even at a
great distance by this means, the great energy which the
brain communicates to the muscles of animal life. The
organic muscular system which stimuli directly applied
put principally in motion, never has exacerbations of
force corresponding to those which the animal contractility
exhibits in so great a degree under certain circumstances.
It is then especially when the muscles move in
virtue of this last property, that the force of their contraction
must be considered. Now this contraction can,
as we have seen, be produced, 1st, by stimulating the
brain in experiments; 2d, when its excitement takes
place in the natural state by the will, or by sympathy.
In the first case, the force of the contraction is never
very powerful, whatever may be the stimulant employed,
either upon the brain, or the nerves laid bare. I have
uniformly observed a very rapid convulsive motion, analogous
to that produced by exciting the muscles themselves,
but never as strong as that which is the result of
vital action. Notwithstanding what some physiologists
have written, we can never by irritating the nerves of
the flexors impart to them an energy comparable to that
which the will can give them. Irritate for example the
sciatic nerve in an inferior extremity which has just been
amputated, the toes will never bend with the force which
they do in certain cases in the natural state. I have
twice made this experiment in amputations performed by
Desault. Unacquainted then with physiology, I was much
struck with this phenomenon.
In the cerebral excitement and in that of the spinal
marrow, we cannot so well appreciate the force of the
contractions which result from it, as when we stimulate
an insulated nerve; in fact, all the system entering then
into convulsive action, the extensors destroy in part the
effort of the flexors and vice versa. The muscles simultaneously
in action, counterbalance, interfere with and
injure each other. The stimulant which gives the greatest
force to the contractions, has always appeared to me
to be galvanism.
In the living state, the force of muscular contraction
depends on two causes; 1st, on the muscle; 2d, on the
brain. These two causes are in a variable proportion;
it is necessary to consider them separately.
Under an equal cerebral influence, a muscle well nourished,
which appears distinctly through the integuments,
and has very large fibres, will contract much more strongly
than that which is delicate, slender, with loose, pale,
small fibres, and which makes but a slight prominence
under the integuments. In our ordinary manner of considering
muscular force, it is to this state of the muscles
that we especially attend. The statues which exhibit
strength and vigour, have always as an attribute a powerful
development of the muscular forms. When the brain
acts upon these muscles with energy they are capable of
extraordinary motions. I shall not relate examples of the
astonishing efforts of which they are susceptible. Haller
and others have cited many of them, either in the muscles
of the back in carrying burdens, or in the muscles of
the superior extremities in raising great weights, or in
the inferior extremities in leaping or in order to preserve
attitudes which suppose enormous resistances to be overcome.
It is especially the cerebral influence that increases
much the force of muscular contraction. The will can
raise this force very high; but the different excitements
that are foreign to it, raise it infinitely more. We know
the force that a man acquires in anger, that of maniacs, of
persons in the cerebral excitement of a fever, &c. In all
these cases the impulse communicated by the brain, is
sometimes such, that the most delicate muscles of the
feeblest woman surpass in energy those of the strongest
man in the ordinary state.
The force of muscular contraction is then in a ratio
compounded of the force of the organization of the texture
of the muscles, and of the force of the cerebral excitement.
If both are slight, the motions are almost
nothing; if both are at the highest degree, it is difficult
to conceive how far the effects may go which result from
them; a maniac with thick and strong muscles is capable
of efforts that we should in vain attempt to calculate. If
the nervous force is very powerful, and the muscular texture
feeble, or if an inverse state exists, the phenomena
of contraction are less. In general nature has almost
always united these two things in this last manner. Women
and children who have a weak fleshy texture, have
a very great nervous mobility; men on the contrary,
those especially with athletic forms, whose nervous systems
are less easily excited, receive more rarely the causes
of a strong influence upon their muscles.
Whatever may be the point of view in which we consider
the force of the contractions of the muscular system
of animal life, it is always very great in proportion to
the effect which results from these contractions. Nature
in the economy follows a law the reverse of that of the
motion of our common machines, the great advantage of
which is to increase the moving powers, to produce a
great effect with a small force. Here there is always a
great expenditure of force for a small effect, which is
owing to the numerous causes that tend to destroy the
effect of this force. 1st. The muscles act almost always
upon a very unfavourable lever, upon that in which the
power they represent is nearer the point of support than
the resistance. 2d. All in contracting have to overcome
the resistance of the antagonists. 3d. As in each motion
there is always a fixed point, the effort which, after contraction,
is carried upon this fixed point, is entirely lost.
4th. Various frictions injure also the motion. 5th. The
obliquity of the insertion of the muscles upon the bones,
an obliquity that approaches nearer a horizontal than a
perpendicular direction, an obliquity not less remarkable
for the fleshy attachments upon the tendon or aponeuroses,
offers a double cause of weakness. All these and
many other reasons which we might with Borelli, who
was the first to make these important remarks upon muscular
motion, add to them, prove that the absolute or real
force of the muscles is infinitely superior to their effective
force. Yet all are not so unfavourably arranged; in
some, as the solæus, the insertion is perpendicular to the
bone; in others, as the muscles which act upon the head,
we observe that they are powers of a lever of the first
kind. In general, in order to estimate the force of a
separate muscle, the deltoid, for example, it is necessary
especially to have regard to the distance of its insertion
at the point of support, to the degree of opening of the
angles formed by the fleshy fibres upon the tendon, and
afterwards by the tendon upon the bone, and to the division
of the forces between the fixed and moveable points.
Some advantages seem to compensate in a slight degree
in certain muscles for their bad arrangement as to the
power of motion; such are, 1st, the sesamoids, the patella,
the different eminences of insertion, the enlargement
of the large bones at their extremities, &c. which remove
the fibres to a distance from the moveable points; 2d, the
intermuscular fat, that which is in the neighbourhood of
the muscles, the fluid of synovial sheaths, which facilitate
motions by lubricating the surfaces that execute them;
3d, the aponeurotic expansions that confine down the
motions on the extremities; 4th, these motions themselves,
those of flexion for example, which, as they take
place, diminish the obliquity of the insertion of the flexors,
and render it even perpendicular, as has been well observed
by a modern author.
Many calculations have been made upon the waste of
muscular motion, upon the effort of a muscle which contracts,
compared with the effect that results from it.
They can never be precise because the vital forces vary
to an infinite degree, because they are not the same in
two individuals and because the cerebral influence and
the force of muscular organization are never in constant
proportion in the same subject. It is a peculiarity of the
vital phenomena to escape all calculations, and to exhibit,
like the forces from which they emanate, a character of
irregularity which distinguishes them essentially from the
physical phenomena. Let us conclude only from the
preceding observations, that the muscular effort carried to
the highest point by cerebral excitement, can produce
astonishing effects, which suppose a force of contraction
hardly conceivable; such is the rupture of the strong
tendons, of the patella, the olecranon, &c.; such is also
the resistance often opposed to the enormous distensions
that are used in luxations, fractures, &c.
The contractions should be considered under the relation
of their quickness as under that of their force.
1st. If it is by stimulants that they are produced, by
laying bare a muscle and acting directly upon it, they
vary according to the state of vitality of the muscle, and
according to the body which stimulates. In the first moments
of the experiment, they succeed with rapidity and
are sometimes connected together with such quickness
that the eye can hardly follow them. As the muscle becomes
weak, its contractions become less prompt; and
they cease at the end of some time. We can reanimate
them by employing a very active stimulant; the fibres
finally become insensible to this also.
2d. If it is by irritating the nerve that we make a voluntary
muscle contract, we produce a still greater quickness
of contraction than by stimulating the muscle itself. Running
would be almost immeasurably rapid, if each contraction
that it requires was equal to those that we thus
obtain, especially when we act on the one hand on very
sensitive animals, and on the other with very active stimulants,
galvanism for example. Upon this subject I have
made a remark, it is that the quickness and the force of
the contractions are not commonly greater if we irritate
at the same time all the nerves that go to a muscle, than
if we irritate but one.
3d. When it is the will that regulates the quickness of
the muscular contractions, this quickness has infinitely
various degrees; but there is always one beyond which
we cannot go. This degree is not the same for all men;
there is even among them in this respect very great differences,
which are foreign to the force of organization
of the muscles; it is rare even that individuals with a
very powerful muscular system are the best runners. I
do not know that we have yet observed the exterior habit
of the body which indicates the quickness of the contractions,
as there is one which denotes their force; it must
however exist. Animals are like men; the degree of
quickness which each can attain, is infinitely variable. I
shall not cite examples of rapid races, of analogous motions
given by the superior extremities, as those of the
fingers in performing on certain instruments, the violin,
the flute, &c.; astonishing ones may be read of in many
authors. I would only remark, that there are but few
motions which give us a greater idea of this quickness,
than the sudden and rapid contractions which, in the inferior
extremities, produce a leap, or that powerful action
of these extremities when we give a kick with the foot;
which in the superior serve for the projection of heavy
bodies; which in the same limbs assist to push the trunk
back, when we support them against a resisting point, and
afterwards suddenly stretch them to push this point forward,
which not yielding, the motion rebounds upon the
trunk; which preside over the action of giving a blow of
the hand; which in the fingers produce the sudden motion,
from which results what is called a fillip, &c. &c. I
confound all these motions almost entirely analogous to
leaping, and which differ from it only in the more or less
evident effects that they produce. Authors, it may be observed,
have not sufficiently established the resemblances
between these various sudden and rapid contractions;
they have considered leaping in too insulated a manner.
But let us return. The degree of rapidity of muscular
contractions is greatly subordinate to exercise. The habit
of making certain muscles act renders them more quick
in their contraction; for example, walking which accustoms
us to contract alternately the extensors and the flexors
of the lower extremities, fits us wonderfully for swiftness
in running. When any man practises for a little
time this last exercise, he soon attains the greatest rapidity
of which his muscular system is capable. On the
contrary, the motions of adduction and abduction being
more rare in the ordinary state, it requires a longer apprenticeship
for dancers to learn to carry their legs rapidly
in and out, for the purpose of executing steps in which
they cross them alternately. In general, habit modifies
much more the quickness than the force of the contractions.
Yet there is always a limit which can never be
passed, whatever may be the exercise that we give to the
muscles; this limit depends on the constitution; each
man is by it, a more or less active leaper and runner.
There is as it respects the duration of the contractions
a remarkable difference in the muscles, according as we
excite these contractions artificially or naturally.
When upon a living animal or one recently killed, we
excite the muscle itself, or we stimulate its nerves, the
relaxation succeeds almost suddenly the contraction;
neither state is ever lasting, though we continue for a
long time the action of the stimulant; the effect which
it has produced is immediately exhausted. When galvanism,
mechanical or chemical agents are used in our
experiments, the phenomenon is the same.
On the contrary, when the will directs the contraction,
it can sustain it for a very long time. The support of
burthens, standing, &c. clearly prove this fact. When
even during life, a morbid irritation is directed upon the
nerves, the contraction can be very permanent, of which
we have terrible proofs in tetanus.
The permanence of the muscular contraction fatigues
the muscle much more than alternate relaxation and contraction.
Hence why when we are standing long, we
contrive by turns to carry the weight of the body more
upon one limb than the other.
Muscles that contract exhibit different phenomena as
follows:
1st. They evidently harden, as we may be convinced
by placing the hand on the masseter, the temporal or any
other superficial muscle in contraction.
2d. They increase in thickness; hence the greater
prominence of all the sub-cutaneous muscles when the
body is in violent action. Sculptors know this difference
very well. A man at rest and a man in motion,
have in their statues an exterior wholly different.
3d. The muscles when they are not confined by the
aponeuroses, sometimes experience a slight displacement.
4th. They diminish in length, and thus the two points
to which they are fixed approximate.
5th. Their volume remains about the same. What they
lose in length, they nearly gain in thickness. Is the proportion
very exact? Of what consequence to us is this
insulated question, to which, since the days of Glisson,
so much importance has have attached! it deserves none.
6th. The blood contained in the vessels of the muscles,
especially in the veins, is in part pressed out; we increase
the flow of the blood by the motions of the arm,
the operation of bleeding proves both these facts.
7th. Yet the muscle does not change colour; it is because
it is not the colouring portion of the blood circulating
with it in the muscular vessels that colours the
muscles, but, as I have said, that which is inherent in
their texture and combined with their fibres; now this
combined colouring substance remains the same in relaxation
and contraction. The heart of the frog is pale
when it contracts; but it is because the blood it contains
is evacuated and the transparency of its parietes renders
this phenomenon evident.
8th. In contracting, the muscles become the seat of
many small transverse wrinkles, sensible especially in
the contractions of oscillation, less apparent in those of the
whole of the muscle, and almost nothing, when a muscle
being laid bare in a living animal, contracts with a small
degree of force.
9th. All authors consider contraction in too uniform a
manner; they have described the phenomena of it, as if
in every case the muscle contracted alike; but it is evident
that there are numerous differences in the state in
which it then is. 1st. There is the slow and insensible
contraction produced by the contractility of texture, when
we cut a muscle or when its antagonist is paralyzed. 2d.
The quick and sudden contraction produced by the will,
or by the excitement of a nerve, a mode of motion that
takes place most commonly either in the ordinary state,
or in convulsions. 3d. The species of oscillation of which
I have already spoken, and which affecting each fibre in
a muscle, does not yet produce any very sensible effect
upon the whole, contracts it a little, but scarcely approximates
at all its moveable points; this is the kind of motion
which takes place in the tremors produced by cold,
by fear, by the beginning of a fit of intermittent fever,
&c. By laying bare a muscle in an animal that is made
to shiver, we see that this kind of contraction resembles
precisely that which is produced by pouring salt in powder
upon a part of the muscular system. Then, although
there may be in all the muscles, an internal motion infinitely
more sensible than in the great contractions, yet
the limbs are displaced but little, there are hardly any
motions of the whole muscles, they are but slight jars.
4th. There are other modes of contraction less sensible
than these, but which however exhibit differences. In
general, to each species of motion of the muscle is adapted
a particular manner of contracting; if we make but
few experiments on living animals, we may easily be convinced
how much the most judicious authors have been
mistaken upon this point.
Two modes of contraction are often combined; for example,
when we cut a muscle transversely in a living
animal, there is at first a slow contraction of the whole,
produced by the contractility of texture, then partial
oscillations in all the divided fibres; now these oscillations
are foreign to the retraction which takes place without
them, often in the living animal and always in the
dead body. So the oscillations can be combined with
the sudden contraction arising from the nervous influence
by the act of the will, or they may be disconnected with
it, as happens almost always when the animal is in full
life. We may be convinced of this last fact without
recourse to experiments, by placing the hand upon the
masseter muscle or the biceps of a thin person when they
are contracting; we do not feel in them through the skin
any motion analogous to these oscillations.
Every muscular motion is either simple or compound.
Let us now speak of the first; by it we shall understand
the second.
Simple Motion.
It must be considered, 1st, in the muscles with a straight
direction; 2d, in those in a reflected one; 3d, in those in
a circular one.
In the first, as in those of the extremities, the trunk,
&c. if they are of an elongated form, and as they terminate
by a tendon, each fibre contracting draws this tendon
from its place; whence it follows that all act together to
bring it towards the centre of the muscle, but at the same
time each of them tends to give it another direction, and
in this respect they are antagonists. The common motion
remains; the opposite is destroyed.
Every effort of contraction in the long muscles is concentrated
upon a single point, the tendon. In most of the
broad muscles, on the contrary, the attachments being
made at two sides by different points, all the fibres do not
contribute to the same end. Thus the different parts of
the same muscle can have very different and even opposite
uses; thus the inferior portion of the great serratus
does not act like the superior; often even the different
portions of the same muscle do not contract at the same
time. In a long muscle, on the contrary, as all the fibres
contribute to produce the same effect, they always act
simultaneously.
To estimate the effect which a muscle in the straight
direction produces upon the bones in which it is inserted,
different means are employed. A very simple one appears
to be that, which I believe has never been mentioned.
It consists in examining the direction of the muscle
from its fixed to its moveable point, and in taking the inverse
of this direction; this last is always the direction
of the motion. Do you wish to know how the anterior
radial acts upon the wrist; take it at its insertion at the
condyle, then follow its direction downwards and outwards;
you will see that it carries the hand upwards and
inwards, that it bends it and places it a little in adduction.
The tibialis anticus directed downwards and inwards
raises the foot and carries it outwards. The anterior rectus
of the thigh going straight from the pelvis to the
patella, raises the leg directly up. All the other muscles
will exhibit this arrangement. Whatever may be the attachment
of their fixed or moveable point, they always
act inversely to the supposed line of direction going from
the first point; and as each attachment can be alternately
moveable or fixed, the two bones which serve them are
carried in an opposite direction; the coraco-brachialis
directed downwards and outwards from the shoulder
towards the arm, carries this last upwards and inwards;
directed from below upwards and from without inwards
from the arm towards the shoulder, it moves this downwards
and outwards. By this general rule, it is sufficient
to see a muscle in a dead body, to pronounce upon
its uses.
When the whole of a broad muscle is united at a common
point, as the deltoid which having many points of
attachment above, is fixed below in a single tendon, the
middle line of direction of all its fibres should be taken
to estimate its uses.
When a muscle is attached by its two extremities at
many points, and consequently the fibres that compose it,
form many fasciculi with different directions and insulated
motions, the line of direction of each fasciculus must
be examined in order to estimate the action of the muscle.
It is thus that we should study that of the trapezius, the
great serratus, the rhomboid, &c.
In the muscles with reflected direction, as the great
oblique of the eye, the lateral peronei, the circumflexus,
&c. the action of the muscle should only be estimated by
the point of reflection; thus the great oblique carries the
eye inwards, though its fleshy portion contracts so as to
carry the moveable point backwards.
The orbicular muscles, those placed around the lips,
the eyes, the anus, &c. have in general no fixed or moveable
points; they are not designed to approximate two
parts to each other, but only to contract the opening
around which they are situated. The anus is shut by its
sphincter, when the excrements do not dilate it. The
mouth remains closed, when the depressors, the elevators
or the abductors of the lips are inactive. The eye is
shut, when the elevator of the superior eye-lid is relaxed.
I would remark upon this subject that the inferior eye-lid
having no depressor, it is principally the other which
contributes to shut or open the eye; and as its muscle
cannot be in permanent contraction, the alterations of its
relaxations produce those continual winkings which take
place when the eye is open; they are to the eye what the
alternate change of the weight of the body from one leg
to the other is in long standing without motion. At
every instant the muscle relaxes; the sphincter acts immediately;
then it contracts and distends the sphincter;
winking then is a continual struggle between the elevator
of the eye-lid and the orbicularis. In sleep, it is not
by the contraction of this that the eye is shut; it is relaxed
like all the muscles; it is because the elevator is
inactive, that the eye-lid falls by its own weight upon the
eye; it communicates as it were the motion to the orbicularis
that it shuts up, whilst, during the day, it is the
orbicularis on the contrary that communicates this motion
to it.
Compound Motions.
There are but few motions in the economy that are simple,
but few muscles that can contract separately. Almost
every sort of contraction supposes another, and for this
reason; the two points to which a muscle is ordinarily
attached are both capable of being moved; if one of
them was not fixed, both would then be put in motion
when the muscle contracted; thus in the contraction of
its extensors, the leg if it was not fixed would approach
the foot as much as the foot approached the leg; now it
could not be fixed but by the muscles which act in an opposite
direction to the effect which the extensors tend to
produce upon it; then whenever the two attachments of
a muscle are moveable, the insulated motion of one of
them supposes the contraction of different muscles to fix
the other.
It is only those muscles that are attached on one side
to a fixed point and on the other to a moveable one, like
those of the eye, and most of those of the face, that can
move in an insulated manner, and without requiring a
motion in the other muscles. It should be remarked however
that in general the contractions destined to fix the
point which should be immoveable in the ordinary motions,
are less than they at first seem to be. In fact, in
these ordinary motions, the point which moves is always
the most moveable, that which remains without motion
is the least so; for example, it requires a much greater
effort in flexors to bend the arm upon the fore-arm, than
to bend the phalanges upon the fore-arm, or the fore-arm
upon the arm. By supposing their two attachments
moveable, the gemelli would act much more powerfully
on the foot than on the femur, &c. In the extremities,
the superior point is always more moveable than the inferior,
now it is this which almost always moves, the
other being fixed; then as it offers more resistance by its
position, it requires less effort of the muscular powers to
retain it. It is only in violent motions, that the previous
contraction of the muscles destined to fix one of the points
of insertion Is very painful. This takes place on the
chest when the trapezius, the great serratus and the great
pectoral contract powerfully; then all the other muscles
of this cavity contract strongly to dilate it, and thus offer
a broader and more fixed attachment to those muscles,
which move the shoulder in the support of burdens, or
in any other analogous effort. The diaphragm contracts
also; hence hernias, the descents which take place from
a concussion in those motions which, at first view, have
no analogy with the abdominal cavity. When in a horizontal
position of the body we raise the head, the rectimuscles
of the abdomen contract to fix the chest, and
present a solid point to the sterno-mastoideus, &c.
We call especially a compound motion that which two
or more muscles, acting upon the same point, contribute
simultaneously to produce. In this case, the moveable
point follows the direction of neither muscle, if there are
two of them, but takes the diagonal of their direction.
It is thus that the eye is moved outwards and upwards,
outwards and downwards, &c.; that the head is depressed,
that it is carried to one side, and that the arm is
applied to the trunk, &c. In general nature has distributed
muscles only in some principal directions around
a moveable point, for example around the eye, in those
of elevation, depression, adduction and abduction; the
combination of these simple motions produces the compound
ones. If the adductor and depressor contract
equally, the eye will be carried exactly in a middle direction;
if one acts with more force than the other, it will
be carried a little nearer the other; so that the four muscles,
by moving separately, or two by two in an equal
manner, carry the eye in eight different directions. In
all the intermediate directions, there is also a simultaneous
action of two muscles, but always a superiority in
the action of one of them. Thus almost all the motions
of circumduction operate.
When two opposite muscles contract, the moveable
part is not moved; they are perfect antagonists. When
two muscles which contract at the same time are placed
in the same direction, there is no loss of power; this is
what takes place when the genio-hyoideus and the mylo-hyoideus
depress the jaw or elevate the os hyoides; these
muscles act completely together. But when two muscles
are in part opposed and in part in the same direction, as
the sterno-mastoidei, one portion of the forces is destroyed
and the other remains. The action by which the sterno-mastoidei
tend to carry the head to the right or the left,
is nothing; that alone by which they direct it downwards
produces its effect which is double, considering the
action of the two muscles, which are thus at the same
time acting together and antagonists. Hence we see that
this applies not only to the motion produced by the contractility
of texture, but also very often to those which
the animal contractility occasions.
When a muscle ceases to contract, it becomes the seat
of phenomena precisely opposite to the preceding, which
it is sufficient to know in order to understand these. The
muscle becomes longer and softer; its wrinkles disappear;
it returns exactly to the state in which it was
found. It is needless to give in detail the series of these
phenomena.
I would remark that in the state of relaxation of the
muscles, the parts often execute motions which are only
owing to their weight; such are the flexion forwards of
the head in sleep, the fall of the fore-arm and the arm in
the same case. Then the weight is often opposed to the
limbs, remaining in their middle position, which are not
supported. We see particularly these phenomena in
paralysis.
The muscular system exhibits great differences, according
as we examine it before the completion of growth, or
in the ages that follow that in which this growth is terminated.
In the first month of the fœtus, this system is, like the
others, a mere mucous homogeneous mass, in which can
be distinguished scarcely any line of demarcation. Aponeuroses,
muscles, tendons, &c. all have the same appearance.
Gradually the limits are established, the muscular
texture at first takes a deeper tinge, from the blood that
enters it. Yet this tinge is at first much less evident
than in the adult; it remains nearly the same till birth.
If we make use of the bones as a means of comparison,
this becomes striking. In the adult the interior of the
bones is less red than the muscular texture; the difference
is remarkable. It is the contrary in the fœtus;
much more blood penetrates the already ossified portion
of the bones, than the interior of the muscles. Nature
distributes the blood in an inverse manner at these two
periods of life in these two systems.
I presume that this phenomenon is principally owing
to the kind of inertia in which the muscles remain before
birth. Observe in fact that though some motions announce
in the last months the presence of the fœtus in
the womb of the mother, yet these motions are infinitely
less than they are to be afterwards. The proof of this is
the constant semi-flexed position which the limbs and
trunk have, and the small space that there is to execute
these motions in, especially in the last periods in which
the waters are wonderfully diminished. In the early
periods of pregnancy, though the space may be greater,
by opening the females of animals, we constantly find
the fœtus drawn up upon itself, and in an attitude almost
immoveable.
Many respectable philosophers have found the muscles
of the chick in its shell much less irritable than after
birth, either by ordinary agents, or by galvanic influence.
I have made the same experiment upon small guinea-pigs
that were never born, by irritating directly their
muscles, or by stimulating their nerves, their spinal marrow
and the brain. The nearer we approach the term
of conception, the less are the motions obtained. That
which is especially remarkable is the rapidity with which,
when the fœtus is dead, the muscles lose their irritability;
the instant that extinguishes life seems to destroy this
property. In the latter periods that precede accouchement,
it is a little more permanent, and more susceptible
of being brought into action, but always less than after
birth. We can hardly doubt then that the motions are
less at this age, though however they exist. We shall
see that the nutrition, size and redness of the muscles are
in general in the adult in proportion to the number of the
motions they perform; it is not then astonishing that less
blood penetrates them in the fœtus. Besides the nearer
we approach the period of conception, the less abundant
is this fluid in them. I have had occasion to make this
remark on guinea-pigs killed at different periods of gestation.
In the early periods, the muscles of the small ones
really resemble those of frogs; white like them, they
are marked with reddish lines, which indicate the course
of the vessels.
I presume also that the kind of blood which circulates
at this age in the arteries and which penetrates the muscles,
is less proper to support and develop their mobility.
In fact it is the black blood that then enters the muscles
by the vessels. We know that in the adult, whenever
this blood circulates preternaturally in the arterial
system, life is altered, the muscular motion is weakened,
and soon asphyxia comes on. It is to the nature and
the colour of the blood of the fœtus, that must be attributed
the livid and often deep tinge that its muscles exhibit;
for this is also a character that distinguishes them
from those of the adult. Not only their colour is less
evident and they are paler, but their tinge is wholly different;
and this tinge has uniformly the character of that
of the fœtus before it has respired.
The muscles are slender, but little developed in the
fœtus. Their development is infinitely less than that of
the muscles of organic life. The size of the limbs arises
especially from their sub-cutaneous fat. When this fat is
in small quantity, and we compare the limbs with the
trunk, they are much less in proportion than they will
be afterwards. In the fœtuses that have much cutaneous
fat, from whom we remove all the skin, we also see this
disproportion of size. We know that at this age all the
cavities of muscular insertion, all the apophyses destined
to the same use, are almost nothing. The parietes of the
temporal fossa, for example, more curved outward, enlarge
the cerebral space, and contract that which the temporal
muscle fills. This is a small anatomical fact which
is the consequence of a great law of nutrition, viz. of the
predominance of the nervous system to which the brain
belongs, over the animal muscular, in respect to development.
Let us remark that this predominance, whence
arises at this age an evident disproportion between the
muscular and nervous systems, when compared to what
they will be afterwards, would alone prove that the muscles
are not, as has been said, a termination and expansion
of the nerves; in fact two species of organs whose
development is inverse, cannot belong to one and the
same system.
Many authors have pretended that the fleshy portion
was in proportion much more developed in the fœtus
than the tendinous, that this even did not exist. I cannot
imagine whence this opinion arose. It may be conceived
that they have thought that the aponeuroses of the limbs
were wanting in the first months; I have uniformly observed
that they have not then that white colour which
characterizes them afterwards, a colour that they only
take when their fibres are developed; they are transparent,
like a serous membrane, and cannot at first sight
be perceived. But the tendons have a very evident
white colour; we distinguish them very well; they are
quite as large and as long in proportion as they will be
afterwards.
At birth, the muscular system of animal life experiences,
like all the others, a remarkable revolution. Until
then black blood only penetrated its arteries; then the
red blood immediately enters them; for this blood is
formed when respiration takes place; now this takes
place in almost all its perfection at the very instant the
fœtus leaves the womb of the mother. We evidently
see besides that the livid tinge of the skin gives place
almost immediately to a red colour, which arises from
this difference of the blood. This new fluid entering the
muscles, is a new cause of excitement, and consequently
of motion. Add to this cause the sudden increase of
cerebral action. Till then, the brain penetrated with
black blood, was as in a kind of inertia, which was principally
owing also to the absence of sensations, as I have
elsewhere proved. Suddenly the red blood enters it; it
stimulates it either by the principles that it contains, or
because it was different from that which had penetrated
it; for such is the nature of sensibility that it is capable
of being affected in an organ, merely because the stimulus
that is applied to it is new. Suddenly excited by the
red blood, the brain re-acts upon the muscles, and determines
them to contract. This cause, joined to the preceding,
appears to me to be one of those which have the
most influence on the sudden disappearance of the kind of
inertia in which the fœtus was, or at least of the small
degree of motion that it performed, by the general agitation
of its limbs, its abdomen, chest, face, &c.; for immediately
after birth all the muscles are moved more or
less strongly.
Let us not, however, exaggerate the influence of a
cause which is certainly not the only one; for example,
the motions of the diaphragm and the pectoral muscles,
are certainly prior to the entrance of the red blood in
the brain, since their action is necessary to the production
of this red blood. These muscles enter into action,
because the excitement of the air on the whole exterior
of the body, and on the mucous membranes in contact
with this fluid, stimulates the brain which is the centre of
all sensation. Moved by this excitement, this organ re-acts
upon the muscles, and begins to make them contract.
The contractions increase, when to this external and indirect
excitement is added the internal and direct excitement
of which we have just spoken. This second excitement
is not absolutely necessary for the fœtus, for we
often see infants that remain livid some instants after
birth, move very well; but in general the motions are
not so decided as when the red colour of the skin indicates
the entrance of the arterial blood, which has undergone
the influence of respiration.
The entrance of the red blood into the muscles does
not give them immediately the colour they will afterwards
have. For some time after birth, they have a
deep tinge, as dissections clearly prove, because, as I
have said, their colour does not come from the colouring
portion circulating in their texture, but from that combined
with this texture. Now nutrition alone produces
the combination; but this function takes place gradually;
it is truly a chronic function, in comparison with exhalation,
absorption, and the circulation, which are evidently
rapid in their progress.
As we advance in age, the muscles assume a redder
tinge; more blood penetrates them; they are nourished
in proportion more than various other organs. This is
particularly remarkable in those of the lower extremities.
I would remark, however, that as long as growth continues,
it is especially upon the length and not upon the
thickness of the muscles, that the energy of nutrition is
carried. Hence why they are but slightly visible through
the integuments and are scarcely at all prominent; why
their forms are rounder and more graceful, but less masculine
at this age. The exterior of a young man is in
this respect wholly different from that of the adult, by
considering each, separate from every cause that can have
an influence upon their conformation. The external appearance
of the infant and the young man is in general
very analogous to that of woman.
Though we do not know so well the difference of the
substances which penetrate the muscles in the first years
and in the adult age, as we know it in the bones in which
the addition of the phosphate of lime to gelatine exhibits
a very striking phenomenon, yet we cannot doubt that
these differences really exist. Treated by ebullition,
combustion, maceration, &c. the flesh of the fœtus does
not give the same results as that of the adult.
The broth made with the muscles of a young animal
contains much more gelatine, a substance which greatly
predominates at this period of life. It has less flavour
than that of adult animals. The extractive substance consequently
appears to be less. A mawkish, nauseous taste
characterizes broths made of veal. The difference of the
principles they contain has an influence even upon the
gastric organs, of which they excite the contraction; they
loosen the belly, as it is called, a phenomenon unknown
to common broths. It does not appear that the fibrin is
in as great a proportion in the muscles at this period of life;
the following considerations make me think so.
1st. Instead of this substance, Fourcroy has found in
the blood of the fœtus a soft texture, without consistence,
and like gelatine; now the blood appears to be the reservoir
of fibrin. 2d. The force and energy of the contractions
are in general in proportion to the quantity of
this principle contained in the muscles; now this energy
is small in the first age. 3d. The muscles burn then,
and crisp and contract less than in the adult. I have
even two or three times seen their texture, when placed
upon live coals, become puffed up like gelatine treated in
the same way.
In general it appears that this last substance occupies
in the muscles the place the fibrous system is afterwards
to hold in them. Those who frequent dissecting rooms,
have observed, no doubt, that other things being equal,
the muscles of young subjects putrify less quickly than
most other substances, and that when they do, they give
out a less fetid odour. We know that broth made of
veal turns sour more easily than that made of beef. It
is always whitish, and never has the deep colour of the
broth made with this last. It becomes like jelly much
more easily. Young and old roast meats exhibit also
great differences. Every kind of stewing either by the
fire alone, or in any fluid, is much quicker and easier in
the first age. The gravy that is then extracted from the
muscles has a character wholly different, it is less strong.
The effects of maceration are also more rapid; we obtain
sooner that mucous pulp, to which the action of water
finally reduces almost all animal substances.
After general growth is finished in length, our organs
then increase in thickness; and it is especially in the
muscles that this phenomenon is remarkable. To the
slender and delicate body and round forms of the youth
and young man, succeeds a large, strong and thick body
with well developed forms. The muscles can be traced
through the integuments, eminences and depressions are
observed in them; different depressed lines serve as
limits to various prominent ones. The animal muscular
system is then more prominent in a state of repose, than
it is in youth in its greatest motions. Painters and sculptors
have studied more than anatomists the different degrees
of the development of the muscles.
The period when the hairs grow, when the genital
organs begin to become active, is principally that in
which the muscles begin to become prominent in man.
In woman, this last period does not present a similar phenomenon;
the muscles preserve the original roundness,
they scarcely ever lose it. In this sex, the roundness of
the limbs, their agreeable forms, make a contrast with the
kind of rudeness of those of man.
The increase in thickness in the muscles appears to be
much more in the fleshy than the tendinous portion, and
especially than the aponeurotic. The intermuscular aponeuroses
principally do not appear to grow in proportion
to the fibres that are inserted into them; so that these
make a prominence, and at the place of the aponeurosis
there is a depression. This is what we see very well in
muscles cut for their insertions by many of these fibrous
expansions, in the deltoid in particular. Not only the
prominence through the skin of the whole of the muscle,
makes the depressions evident that separate it from the
others, but each fleshy bundle has a prominence which a
groove separates; this, it is true, is only distinguishable
upon thin subjects.
As the muscle grows in thickness, it increases in density.
It becomes firmer and more resisting. If we place
for comparison the hand upon two similar muscles of an
adult and an infant, whilst they are in contraction, we feel
a sensible difference in their hardness. Weights suspended
for comparison to the muscles of the two ages, taken
in the dead bodies, prove the different degree of their
resistance. The muscular texture of adults yields more
slowly to all re-agents.
The colour of the muscles continues to be red in the
adult; but in general, and all things being equal in respect
to the causes that make this colour vary, it begins
to become of a less bright red after the thirtieth year.
It is usually in the last years of growth, and even from
the tenth to the twentieth, that the colour is the most
brilliant.
In the adult this colour exhibits a very remarkable phenomenon.
All men have their muscles red, but hardly
two have the same shade. Those who have opened
many dead bodies are easily convinced of this; a residence
at the dissecting rooms proves this assertion. A
thousand causes have an influence upon this colour; the
temperament is the principal. The external appearance
of the muscles without the skin indicates by their shades
of colour the temperament, as well as the integuments
do. Diseases make this colour vary wonderfully. All
those that have a chronic progress alter it remarkably;
it then becomes pale, dull, &c. Dropsies whiten it, when
they are of long standing. In general, every thing that
has upon the powers of life a slow and debilitating influence,
diminishes the brightness of it. Acute diseases,
whatever may be their nature, change it but little.
Fevers with the greatest prostration, if they suddenly
produce death, leave it untouched, because this colour can
only change by nutrition; now as this function is slow in
its phenomena, it is but little affected by acute diseases;
it is only at the end of some time that it feels the affections
reigning in the economy.
I would observe that the varieties of colour that are
seen in the muscles of adults, even in the healthy state,
distinguish them especially from those of the fœtus, which
have in general an uniform paleness. This difference
is owing to the fact, that in the first age, we are not
subject to the action of the numerous agents which modify,
in an infinitely variable manner in the after ages, the
great functions, and of course nutrition which is the end
of them. It is in these varieties of colour of the muscular
system of the adult, that we clearly distinguish that
the blood circulating in the arteries is wholly foreign to
it; in fact it is uniform, and never partakes of those
varieties of colour whatever they may be.
Many circumstances in the adult make the muscular
nutrition vary; motion is the principal. The man who
passes his life at rest is remarkable for the small prominence
of his muscles, especially if we compare this
prominence with that of the muscles of a man who takes
great exercise. Not only general motion exhibits this
phenomenon, but also local motion, as we see in the
arms of bakers, the legs of dancers, the backs of porters,
&c.
In old age, the texture of the muscles changes remarkably;
it becomes resisting and stiff; the teeth tear it with
difficulty. This too great density is injurious to its contractions,
which can now only take place slowly; the
action of the brain becomes less upon the muscles; the
continuance of their motions is not as long; they are
sooner fatigued.
I would remark that the density of the muscles should
not be confounded with their cohesion. The first arises
from substances that enter into the composition of the
muscle. Cohesion on the contrary appears to be owing
to vital influence, the effect of which is preserved after
death. Dissect the muscles of a strong and vigorous
adult; the fleshy mass is firm; it keeps in its place; it
supports itself, though the scalpel may have removed
from it every surrounding texture. On the contrary
in a body dead of a chronic disease, in a dropsical or
phthisical subject, the muscles are loose and cannot support
themselves; the relations are destroyed when the
surrounding texture is removed. The first subjects are
much more suitable for the dissection of myology than
the last. The muscular texture is in old subjects nearly
as in these last, flaccid and loose; we feel this flaccidity
under the skin in the solæus, the gemelli, the biceps, &c.;
it does not prevent each fibre from being dense and
tough. In general the muscular cohesion is in the inverse
ratio of the age; the muscles of a young man are
firm and compact; they are not moveable under the skin.
Towards the fortieth year and afterwards, we begin to
perceive more laxity; the calves of the legs vacillate in
great motions; the glutei and in general all the prominent
limbs exhibit also this vacillation, especially if the
individual is thin. The muscles become more and more
susceptible of moving thus, as we approach old age, a
period in which the least motion makes the whole muscular
system vacillate. Why? Because the muscle is no
longer in sufficient contraction; it is as it were too long
for the space it fills. This appears to be owing to the
circumstance that the contractility of texture has diminished
in the last age; we can be convinced of this by
cutting transversely for comparison a muscle in an old
man and a young one; it retracts more in fact in an opposite
direction in the second than in the first. This contractility
of texture approximates all the particles of the
muscle when at rest; it can no longer produce this approximation;
the muscle remains loose. Authors have
not sufficiently observed this remarkable phenomenon
which the muscular system experiences from the progress
of age, a phenomenon which is really the index of
its degree of contractile power.
Frequently in old age the muscular texture loses its
colour and takes a yellowish one and has a fatty appearance,
though however this colour does not arise from the
fat, but from the absence of the colouring substance of
the blood. I have often made this remark. If we strip
all the surrounding fat from these pretended fatty muscles,
and leave them only their texture, combustion or
ebullition extracts no animal oil from them; they are in
their fibrous state as usual; the colour only is different. I
have remarked that the deep muscles of the back and those
placed in the vertebral depressions are much more subject
than all the others to lose their colour and to exhibit this
yellowish aspect, an aspect that is rarely ever seen in the
whole system, but only in some insulated muscles. Adults
are subject, though less frequently however, than old people,
to this alteration. Many times we see limbs that are
poorly nourished, with an aspect, nearly the same. In
recent palsies, in those even of three, four or six months,
there is in general no change in the limbs; the muscles
preserve their colour and their size; but at the end of a
longer time, the absence of motion, perhaps also the deficiency
of nervous influx, terminate by altering the nutrition
left for a long time untouched without this influx,
and then the muscles change colour, contract and diminish.
But this phenomenon is not always constant, and
there are at the Hôtel-Dieu hemiplegias of six, seven
and even ten years, without the limb of the sound side
predominating in its nutrition over that of the diseased
one.
External pressures for a long time continued upon a
muscle, produce nearly the same effect as want of nourishment;
they discolour and whiten it by preventing the
circulation in it. Those who make use of straps constantly
passed under the arms, who habitually have
girdles round the abdomen and who lift burdens, have
often the muscles corresponding to the constant pressure
they experience, in the state of those of old people. I
would remark that these muscles contract notwithstanding;
which proves that the colouring substance is not of absolute
necessity to muscular action.
The blood is carried in general in much less quantity
in the muscles of old people; their vessels are in part
obstructed; this is what disposes them to the state of
which I have just spoken.
At the instant of death, the muscles remain in two
different states; sometimes they are stiff and inflexible;
sometimes they allow the limbs to execute motions very
easily. It is sometimes necessary to make an effort to
bend the thigh of a dead body; at others the least touch
is sufficient to do it, as for example in asphyxia, from
charcoal. These state of rigidity and relaxation have infinite
degrees. The first is sometimes so great, that the
subject raised against a wall remains standing; at other
times it is nothing. Some muscles are stiff in subjects,
while others are relaxed. It appears that these different
states depend upon the kind of death, upon the phenomena
that accompany the last moments. But how do they
precisely happen? It is an object of interesting research.
I have remarked that the muscles remaining stiff at the
instant of death, are often torn with ease, if we attempt
to force the motions of the limbs to which they go; that
the tearing hardly ever takes place on the contrary in
those remaining supple, whatever may be the impulse
communicated at their moveable points; it is necessary
to draw them directly, attach weights to them, &c. to
produce this phenomenon, which is then easy.
The muscular texture is never preternaturally developed
in the different organs in which nature has not
originally placed it, as happens in the osseous, cartilaginous
and even fibrous textures. If it were developed, it
would not belong to animal but to organic life; because
in order to depend upon the first, the cerebral nerves are
essentially necessary, the muscle being but the agent of
the motions which the latter communicate.
END OF VOL. II.
