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.