intestines, and empty it entirely of the substances that it contains,
it contracts and dilates alternately as when it is full, if we apply an
external stimulant to it. 2d. If we empty by punctures all the great
vessels which go to the heart, or come from it, so as to evacuate it
entirely, its alternate dilatations and contractions continue for some
time. 3d. In order to judge comparatively of the degree of force of the
contraction and the dilatation, we can extract two hearts nearly equal
in size from two living animals; place immediately the fingers of one
hand into the auricles or the ventricles of the first, and grasp with
the other hand the exterior of the second; you will feel that one makes
as great an effort in dilating as the other does in contracting. This
fact already observed by Pechlin, is so much the more remarkable, as
the effort of dilatation is often greater than that of contraction. I
have even observed, in repeating this experiment, that whatever effort
we make with the hand, we cannot prevent the organ from dilating.
4th. The alternate extension and contraction, from which arises the
vermicular motion of the intestines, is seen during hunger when we open
the abdomen of an animal. 5th. The hardness of the organic muscular
texture is as evident during dilatation as during vacuity. 6th. I
have many times observed that at the instant in which I irritated the
heart with the point of a scalpel, that a dilatation was the first
consequence of it, and that contraction was only consequent to it.
It happens in general more often that contraction begins the motions
in our experiments; but certainly, the muscle being at rest, it is
frequently a dilatation that first manifests itself.
It appears then very probable that the dilatation of the organic
muscles is a phenomenon as vital as their contraction; that these two
states are united in a necessary manner; that both of them compose
muscular motion, of which contraction is but one part. Who knows even
if each may not be disturbed separately, if to a regular contraction
may not succeed an irregular dilatation and vice versa? Who knows
if certain alterations in the pulse do not belong to injuries of
dilatation and others to those of contraction? I am far from being
certain; for in medicine we must rest our belief on certainty and not
on presumption; but we can make this point an object of research.
It appears that sometimes the voluntary muscles are also the seat of
a true active dilatation. 1st. A muscle, laid bare and extracted from
the body, contracts and afterwards dilates, without being drawn to this
state of dilatation by any cause. 2d. In an amputation, we often see
in the stump the end of the divided fibres alternately lengthen and
contract; a double motion both of which appears to be equally vital.
3d. In many kinds of convulsions in which the extremities stiffen, in
those, for example, which accompany most hysterical fits, it appears
that there is a very evident active dilatation; by placing in fact
the hand upon the muscles which should then be relaxed, from the
disposition of the parts, we perceive a hardness as great as in feeling
of the contracted muscles.
There are many researches to be made upon this mode of dilatation of
our parts, a mode which undoubtedly is not exclusively confined to
the muscular system, but which appears to belong also to the iris, to
the spongy texture of the corpora cavernosa, to the nipples, &c. All
these organs move by dilating very evidently; contraction succeeds in
them expansion, as in the common muscles relaxation does contraction.
Expansion is the principal phenomenon. Perhaps also, as some modern
authors have thought, the sudden swellings of the cellular texture,
which accompany contusions, bruises, &c. are the result of this mode of
motion.
ARTICLE FIFTH.
DEVELOPMENT OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.
The organic muscular system is wholly the reverse of the preceding,
as it respects development. This is but slightly characterized in the
early ages, whereas the growth of the other is precocious. Let us
follow it in all the ages.
I. _State of the Organic Muscular System in the Fœtus._
In the first days after conception, the heart is formed; it is the
first point of motion, a punctum saliens, as it has been called. The
researches of different authors, of Haller in particular, have rendered
clear the successive progress of its increase in the early periods.
Rather late in their formation, the muscles of the interior of the
abdomen are yet developed before those that form the parietes of this
cavity. It is the size of the intestines, the stomach, the bladder, &c.
almost as much as that of the liver, which gives to the cavity in which
these viscera are found, the remarkable capacity that it then exhibits.
Nearly uniform at this age, as it respects the proportion of their
size, all the organic muscles are not as much so in regard to that of
their texture. The heart is evidently firmer and more dense than all
the others; its texture is very distinct. The fibres of the stomach,
intestines and bladder are soft and loose and resemble exactly those of
the muscles of animal life; but little blood goes to them in proportion
to what they are afterwards to receive. The fibres of the heart, on
the contrary, dense and compact, have a power of action in proportion
to what they are afterwards to have. Their redness is as distinct; as
much blood penetrates and consequently nourishes them. This redness of
the heart, analogous in the adult to that of the voluntary muscles,
forms at this period a contrast with the remarkable paleness of these
muscles. Besides it has, as in all the other parts where it exists, a
deep tinge, owing to the kind of blood that produces it.
We easily see the reason of the quantity of blood that penetrates the
heart, as this organ then very active in its motions, has need of much
force, whilst the others, almost immoveable, require but little.
Yet the sensible organic contractility of the heart in the fœtus and
in the first age has been exaggerated, undoubtedly on account of the
extreme rapidity that the circulation then exhibits. This rapidity
depends as much on the activity of the tonic forces of the general
capillary system, as on that of the heart; for the blood, when it has
arrived in the capillary system, is wholly beyond the influence of
the heart, as we have seen; the stay that it makes there is wholly
dependant upon the forces of the system itself; now these forces, at
that time very active, accelerate the course of the blood, and send
it into the venous system, from which it goes to the heart. If the
excitability of this were double and even treble, and the blood entered
it but slowly, it would be unable to support a rapid and at the same
time continuous pulse. Haller was drawn to this opinion by believing
that the heart was the only agent of impulse of the blood circulating
even in the small vessels. Besides, there is no doubt that the sensible
organic contractility of the heart is less easily put into action by
experiments in the fœtus, and that it is also much less durable. Then
the strongest stimuli have less effect upon it an instant after death,
than those of less power exhibit upon the heart of an animal that has
been born. I have many times established this fact upon fœtuses of
guinea-pigs. Compared with that of the voluntary muscles, the mobility
of the heart is undoubtedly remarkable in the fœtus; but compared to
what it will be after birth, it is but slight.
It is precisely the same with the contractility of the stomach, the
bladder and the intestines; most commonly we can produce no motion in
these muscles by stimuli. Mr. Léveillé has already made these important
observations; he has also remarked that the urine remained in the
bladder, and the meconium in the great intestines, without producing a
contraction sufficient to expel them. I do not think however that there
could be during life a complete immobility of the gastric viscera,
and for this reason; most commonly the meconium is only met with in
the great intestines; it must have been formed in them then, if there
was complete immobility of the gastric muscles; now it is much more
probable that it is the residuum of the bile, of all the mucous juices,
&c.; that consequently it has been pushed successively by a slow action
from the superior part towards the inferior of the alimentary canal.
The softness of the organic muscles renders their extensibility of
texture very great at this period. I would observe however that the
hearts of dead fœtuses do not exhibit those numberless varieties of
size which those of adults do in the right side, according to the
different kinds of death.
II. _State of the Organic Muscular System during Growth._
The first days of existence are marked by an internal motion as quick
in manifesting itself as the external of which we have spoken. The
sucking of the milk, the evacuation of the urine and meconium, &c.
are indices of this general internal motion, of this agitation almost
sudden of all the involuntary muscles.
It is not the brain which, entering into action at birth, produces the
contraction of these muscles, since as we have said they are not under
its government; it appears to depend, 1st, on the sympathetic influence
exerted upon their system, by the cutaneous organ, which is irritated
by the new medium; 2d, on the excitement made upon the beginning of
all the mucous surfaces, and upon the whole of that of the lungs, an
excitement which afterwards reacts upon these muscles; 3d, on that
produced by fluids introduced into the stomach; 4th, on the sudden
entrance of the red blood into all these muscles, till then penetrated
like the others with black; this cause is essential; irritability
appears to be in part dependant on it, or at least to borrow from it a
remarkable increase of force; 5th, the excretion of the meconium and
the urine is also powerfully assisted by the abdominal muscles, which
then enter into activity with the whole system to which they belong.
The general internal motion which takes place in the first moments of
existence, and which is produced by the suddenly increased activity
of the involuntary muscles, has an important use with respect to the
mucous surfaces, which it relieves of the fluids that load them,
and whose presence becomes painful. Where the mucous surfaces have
not around them fleshy layers of the involuntary muscles, as in the
bronchia, the nasal fossæ, &c. the muscles of animal life more or less
distant, perform this function, as for example, the diaphragm and the
intercostals, free the bronchial surface by coughing, and the pituitary
by sneezing.
As we recede from the period of birth, the organic muscles grow in
general much less in proportion than the others; it is this that
gradually re-establishes the equilibrium between the two systems. I
would remark however, as it respects the predominance of the first,
that it is much less conspicuous in the fœtus than that of the nervous
system. The brain, for example, is in proportion much larger than the
heart.
It is probable that the muscles of which we are treating, exhibit, at
this period, the same varieties of composition as the others, that
gelatine especially predominates in them, that they have less fibrin,
&c. This last substance perhaps exists, in the early periods, more
abundantly in the heart than in the other muscles of this class.
We have observed two very distinct periods in the growth of the
other muscles; one is finished when they have acquired their length;
the other, when their thickness is complete. The first has not, in
the organic system, a term as distinct; when the stature no longer
increases, the gastric and urinary organs, and the heart still lengthen
and grow.
We have considered growth in too general a manner. Each system has
a different term in this great phenomenon. The osseous and muscular
systems of animal life, and those which depend on them, as the fibrous,
the cartilaginous, &c. have especially an influence upon the general
stature of the body; it is these which produce this or that height; but
this height has no influence upon the length of the intestines, or the
capacity of the stomach, the heart, the bladder, &c. The glandular,
serous, mucous systems, &c. are equally independent of stature; thus
in these numerous varieties, it has much more influence upon the
extremities, than upon the abdomen, the thorax, &c. A great height
indicates the predominance of the apparatus of locomotion, but not of
those of digestion, respiration, &c. The termination of the growth in
height, which we consider in a general manner for the whole body, is
only the termination of the growth of the muscles, the bones and their
dependancies, and not of that of the internal viscera, which still
lengthen and become thicker. It is easy to be convinced of this, by
comparing the organic muscles of a young man of eighteen years, with
those of a man of thirty or forty.
The organic muscles do not appear to be subject to those irregularities
of growth which the other muscles and the bones frequently exhibit.
We know that the stature often remains stationary for many years,
and that suddenly it acquires very great dimensions in a very short
time; this phenomenon is remarkable especially after long diseases.
Now notwithstanding these inequalities, the heart and all the other
analogous muscles grow in an uniform manner; the regularity of the
internal functions to which these muscles especially contribute, could
not adapt itself to those aberrations which would be unable to disturb
the functions of the locomotive organs. Besides, if they took place,
the circulation, digestion, excretion of urine, &c. would exhibit
corresponding aberrations; now this is never observed. The heart and
the gastric muscles, &c. always grow in an infant whose stature remains
stationary; they do not grow suddenly in one who grows at once; hence
why the thorax and the abdomen become large in the first case, and
remain contracted in the second in proportion to the extremities.
Besides these two systems are never in precise relation of nutrition
and power. I have already observed that very large organic muscles
often exist with very small voluntary ones, and vice versa.
Let us consider neither the growth nor nutrition in an uniform manner;
each system is developed and increases in its own way; all are never
found at the same periods of this function. Why? because nutrition,
like all the other acts over which life presides, is essentially
dependant on the vital forces, and these forces vary in each system.
The growth of the involuntary muscular system is not uniform in all the
organs which compose it. Each increases more or less, or is differently
developed; one often predominates over the others in an evident manner;
a bladder with strong, fleshy fibres, with columns as they are called,
is often found in a subject with a debilitated stomach, with small
intestines, &c.; reciprocally, the stomach, the heart, &c. have often
an insulated predominance.
III. _State of the Organic Muscular System after Growth._
It is from the twenty-fourth to the twenty-sixth year, that the organic
muscles are completely developed. Then the thorax and the abdomen which
contain them have their greatest capacity. These muscles are then as
they are to remain through life; they have a density much greater
than in youth; their power is increased and their colour is deeper.
In general this is subject in the heart to frequent varieties, which
coincide very nearly with the varieties of the preceding system. Acute
and chronic diseases have nearly the same influence upon it. It is
equally the index of the sanguineous, lymphatic temperaments, &c. by
the different tinge it assumes. The colour of the gastric, intestinal
and vesical fibres varies less; their whiteness, more uniform, is
rarely influenced by diseases.
We cannot increase, by constant exercise, the nutrition of the organic
muscles. Aliments taken beyond measure, making the stomach frequently
contract, weaken it instead of developing its fibres more, as happens
from constant exercise given to a superior or inferior extremity. The
bladder incessantly in action in some cases of incontinence, is thus
gradually weakened and loses its energy. We might say that these two
systems were in this respect in an inverse order.
It appears that the nutrition of the organic muscles, like that of
the others, is subject to frequent variations; that at some periods
they are more developed and less so at others. Diseases have a great
influence upon this phenomenon, which proves, like the softening of the
bones and their return to the natural state, the constant composition
and decomposition of which these organs are the seat. We find in the
dissecting rooms many differences in different subjects, as it respects
the colour, density and cohesion of the muscles. Now what many exhibit
then at once, the same individual often experiences successively; the
same man no doubt has, according to the different influences to which
he is exposed, his heart red, dense, large and well nourished at one
period of life, and feeble, pale and small at another; for the internal
organs experience the same alterations as the exterior. Now we know
that the external appearance often changes during life.
IV. _State of the Organic Muscular System in Old Age._
As we advance in age, the muscular system of which we are treating
becomes weak like all the others; yet its action is more durable;
it survives, if we may so say, that of the other. When the old
man, almost immoveable, crawls about but slowly and with pain, his
pulse, digestion, &c. have vigour still. This difference of the two
systems is so much the more remarkable, as the time of activity of
the second is almost by half less than that of the first; sleep cuts
off in fact almost half of the duration of the voluntary motions,
whilst it leaves the involuntary wholly untouched. This phenomenon of
the organic muscles as it were surviving the voluntary in the last
periods of life, is derived on a great scale from the same principle
from which arises on a small one the lassitude which follows the
contraction in an insulated motion. A less durable motion is necessary
to fatigue the voluntary muscles, than to fatigue the involuntary; the
stomach empty remains for a long time contracted upon itself without
producing any painful sensation, whilst if we hold a body strongly
grasped between our fingers for a quarter of an hour, all the flexors
are soon painfully affected. After a convulsion of half an hour, in
which all the locomotive muscles have been stiff, the whole body is
broken, as it is called; it cannot admit of any motion; whilst after
a paroxysm of fever of six or eight hours in which the pulse has been
violently agitated, the heart often preserves the natural type of its
contractions; it requires repeated paroxysms to weaken it. All these
phenomena of the two muscular systems evidently prove that that of
animal life is fatigued much the soonest; it is this which occasions
its intermission. Is it then astonishing that, although less often in
exercise than the other, it exhausts sooner the quantum of force nature
has given to it? is it astonishing that the other survives the longest?
Life is a great exercise which gradually wears up the organs in motion,
and which requires their rest; this rest is death; now each moveable
organ arrives at it sooner or later, according to the different degree
of the forces which it has to expend, and according to its greater or
less disposition to be wearied by this great exercise.
Yet the organic muscles are gradually weakened. The pulse becomes
slower, digestion is longer in old age; the bladder and rectum first
cease to act; then the intestines remain inactive; the stomach and
especially the heart die the last.
A long time before death, the muscular cohesion is weakened in this
system as in the preceding; the fleshy texture becomes flaccid; the
parietes of the heart support themselves in youth; they flatten in
old age. The gastric system of a young animal suddenly killed during
hunger is firm, dense and contracted upon itself; in an old one, under
the same circumstance, it is but little contracted; the stomach and
intestines remain much more dilated; they are loose and soft; it is
the same phenomenon as in the preceding muscles, which vacillate under
the skin, from want of cohesion. The bladder remains constantly large,
though empty.
MUCOUS SYSTEM.
This system, the name of which I borrow from the fluid that constantly
lubricates it, and which is furnished by small glands inherent in its
structure, appears everywhere in a membranous form; that of fasciculi
is wholly foreign to it. In speaking of the mucous organs we shall
designate them almost always under the name of membranes. Their study
is a new object of research. Pinel has been among the first, who has
perceived the necessity of considering them in a general manner as
it respects diseases. I believe that I am the first who has regarded
them generally in an anatomical and physiological view. Few systems
deserve more attention; upon it take place all the great phenomena of
digestion, respiration, secretion, excretion, &c.; it is the seat of
many diseases. It should alone, in a nosography in which diseases are
distributed by systems, occupy a place equal to that of many.
ARTICLE FIRST.
OF THE DIVISIONS AND FORMS OF THE MUCOUS SYSTEM.
The mucous membranes occupy the interior of the cavities which
communicate with the skin by the different openings this covering
has on the surface of the body. Their number at first view is very
considerable; for the organs in which they are reflected are very
numerous. The mouth, the stomach, the intestines, the œsophagus, the
bladder, the urethra, the womb, the ureters, all the excretories, &c.
&c. derive from these membranes a part of their structure. Yet if
we consider that wherever they are continuous, wherever we see them
originate, by extending from each other, as they originated in the
first instance from the skin, we shall perceive that this number must
be wonderfully limited. In fact by thus describing them, not separately
in each part, but at the same time in all those upon which they are
continued, we see that they are reduced to two general surfaces,
of which all the others are portions, and which, on account of the
different parts to which they are distributed, can be called, the one
gastro-pulmonary, the other genito-urinary. The first is found in the
head, the neck and the abdomen. This last cavity and more especially
the pelvis, contain the second.
There is also a small insulated mucous surface; it is that which enters
by the openings of the nipples and lines the lactiferous tubes. But it
is so small that it deserves but little attention; besides, what will
be said of the two others will be equally applicable to it. It is then
useless to examine it in a general manner.
I. _Of the two General Mucous Membranes, the Gastro-Pulmonary and the
Genito-Urinary._
The gastro-pulmonary surface penetrates into the interior by the mouth,
the nose and the anterior face of the eye. 1st. It lines the first and
second of these cavities, extends from the first to the excretory ducts
of the parotid and sub-maxillary glands, from the other into all the
sinuses, forms the conjunctiva, dips down into the puncta lachrymalia,
the nasal duct, the sac of the same name, and is continued into the
nose; 2d, it descends into the pharynx, furnishes an elongation to
the Eustachian tube, then penetrates the internal ear and lines it, as
we shall see; 3d, it dips down into the trachea and is spread upon all
the air-tubes; 4th, it penetrates into the œsophagus and the stomach;
5th, it extends to the duodenum where it furnishes two elongations,
one destined to the ductus choledochus, to the numerous branches of
the hepatic and cystic ducts and the gall-bladder, the other to the
pancreatic duct and its different branches; 6th, it is continued into
the small and large intestines and finally terminates at the anus where
we see it identified with the skin.
The second general mucous membrane, which we have called the
genito-urinary, enters in man by the urethra, and thence is spread on
the one hand upon the bladder, the ureters, the pelvis of the kidnies,
the infundibula, the papillæ and the capillary tubes which open on
their summit; on the other hand it goes into the excretory tubes of
the prostate, into the seminal ducts, the vesiculæ seminales, the vasa
deferentia and the branches with numberless windings that produce them.