but without taking the yellowish colour of the fibrous texture; it
remains white. When it is dried in considerable layers, its cells
adhere together, and these layers being stretched a little to
facilitate the drying, represent a true serous membrane, so that it
would be impossible to distinguish it from one dried in the same way.
In this state the cellular texture is pliable; it can be bent with
great ease in every direction; it has not the stiffness of dried
fibrous texture; when immersed again in water, it takes but imperfectly
its former appearance; its cells are separated with difficulty.
Exposed to putrefaction with other animal substances, it yields to it
less readily than many of them, for example, than the glandular and
muscular organs; filled with the putrefactive juices it does not become
pulpy until some time after these parts. This fact is particularly
remarkable in the sub-mucous texture, in that which surrounds the
vessels; the filaments that compose it, resist much longer than the
other parts of the cellular system, the putrefactive process.
The same may be said of maceration as of the preceding phenomena.
In looking at a tendon and a portion of cellular texture, who would
say that the action of water would soften the first quicker than the
second? the one being soft and almost fluid, and the other compact.
After remaining in water three months, of the temperature of a cellar,
the cellular texture of the arteries did not appear to me to have
undergone any alteration. The sub-cutaneous, the sub-serous, the
intermuscular textures, &c. are changed sooner, but not so soon as
that of some other organs. I have kept for six months, in a glass
vessel, some nerves, which as we shall see, are not altered in water;
the texture which separated the fibres of these, was as firm and
distinct as at first. This resistance to the action of water is less,
when the cellular texture is macerated with organs that soon yield and
become pulpy, than when it is exposed alone. This resistance is the
more remarkable, as this texture, being very fine, is accessible at
many points to the contact of the fluid. If the texture of tendons, of
cartilages, of aponeuroses, of the skin, &c. was arranged in layers as
fine and as much separated, I am satisfied that three or four days of
maceration would be sufficient to reduce them to a mere pulp.
As much may be said of ebullition; a few minutes would be sufficient to
dissipate and melt into gelatine most of the white textures, if they
were arranged in layers as fine as the cellular system; this, however,
resists a long time; different layers are still seen between the fibres
of the boiled muscles. The fat which remains in parcels among the
fleshy fibres, after the boiling, would have been melted, if it had not
been contained in cells which continue untouched; we can, moreover,
be easily convinced of the existence of these layers in the parcels
of fat. It is especially upon the texture exterior to the arteries,
the excretories, &c. that the action of boiling water is longest in
producing an effect.
The cellular texture that is boiled exhibits phenomena analogous to
other organs treated in the same way. 1st. At the instant of boiling,
when an albuminous froth rises upon the water that contains it, it
remains soft, and about the same it was at first. 2d. When this
froth is formed, it becomes hard, is crisped and contracted in size.
The hardening increases until it boils, which takes place almost
immediately. In this state the texture is firmer; it has become
elastic; if drawn in an opposite direction, it suddenly returns, which
it would not do before. 3d. Ebullition being continued, it gradually
softens and loses the hardness it had acquired; then it can hardly
be extended at all; it may be much elongated without breaking, in a
natural state, the rupture of it is now the effect of the least effort.
4th. In fine, by the continued action of boiling water, it gradually
melts. I have remarked, that it does not in any period of ebullition,
assume the yellowish tinge, which is spread over the whole of the
fibrous system when boiled.
From the phenomena that cellular texture offers when exposed to the
action of dry and moist air, of cold and boiling water, &c. I presume
that it is less easily changed by the gastric juices than many others,
the muscular texture, for example; besides, the following facts prove
this. 1st. The taste, almost always a certain index which nature has
given us to judge of digestible aliments, is much less gratified with
the cellular texture that is mixed with cooked meat, than with the
meat itself. 2d. I have made this experiment upon myself; when my
stomach contained a sufficient quantity of food, I excited vomiting
nearly an hour after eating; when it contained but little, I could not
vomit without taking a large quantity of warm water; I then threw up
this and with it the aliments the stomach contained. I have frequently
ascertained by these means, especially by the last, that the cellular
lumps which are found with the fleshy fibres of boiled meat, are much
longer in being altered than the fibres themselves; these last have
become pulpy before the others are acted upon. The fat, which generally
fills these cellular lumps, may have an influence also in this
phenomenon. 3d. I have made the same observation upon dogs that I have
opened at different periods of digestion to determine the difference of
the bile in the cystic and hepatic ducts, a difference of which I have
already given some account.
How can the cellular texture unite to the softness and delicacy that
characterize it, a greater resistance to the different re-agents, than
that of other textures much more firm?
We know that in those who are drowned, a great quantity of gas
disengaged from different organs, from those especially that contain
much blood, as the muscles, the glands, &c. fills the cellular
texture, renders it emphysematous and makes the body float. This
does not so often take place in the open air, where putrefaction is
sudden and where there is a discolouration and disorganization of
parts. The tendons, the aponeuroses, the cartilages, the bones, &c.
have appeared to me in animals drowned for the purpose, not to assist
in the production of this gas. The cellular texture itself has less
part in it, I think, than the organs before pointed out. It would be
easy to know the kind of gas that each organized system furnishes, by
macerating these systems separately in closed vessels, so arranged that
their aeriform products might be collected. If each has a peculiar mode
of putrefaction and gangrene, &c. if in this state their appearance is
different, it is presumable that the products that escape from them are
also different.
In dead bodies that are buried, and beyond the reach of the air, the
emphysematous swelling often takes place, and it is sometimes so
powerful, as I have observed in a church-yard, that it will raise the
lid of the coffin, though it may be covered with half a foot of earth,
which raises it then above the level of the earth that covers the other
coffins.
II. _Parts common to the organization of the cellular system. Blood
vessels._
We must not judge of the vessels of the cellular texture by injections.
When they are fine and have succeeded well, a thousand different
threads interlaced in every way, destroy its whitish colour and change
it into a vascular net-work. The appearance of a body thus injected
is deceptive; it arises from this, that the exhalants have admitted a
fluid forced through the arteries, whilst their own sensibility would
repulse the blood in an ordinary state. In dissecting the cellular
texture upon a living animal, it is seen to be white as in the dead
body, and that great trunks that do not belong to it, send off in
passing through it different branches and ramifications that are
evidently lost in it. In raising the skin from the subjacent organs,
the sub-cutaneous texture is distended, and we may clearly distinguish
in it different little branches that end there; this is remarkable
in dogs. By first making the cellular texture emphysematous, the
experiment succeeds better. We see, also, very well in this way, that
the blood varies in the vessels; often after being exposed sometime to
the air, there appears double the number of them there was when it was
laid bare. There are always remarkable variations, if the place that
is denuded is examined even for a short time; it is the blood retained
in the exhalants, and it seems thus to increase the number of little
arteries.
_Exhalants._
The existence of the exhalants is rendered evident, 1st. by the
preceding experiment, which is a natural manner of injecting them; 2d.
by artificial injections, which shows there many more vessels than
ordinary; 3d. by transudations that sometimes take place in the cells,
when these injections are driven with much force, transudations that
really form an artificial exhalation; 4th. by natural exhalation, which
is continually going on, and which has for its materials the fat and
the serum; 5th. by accidental exhalations that sometimes take place, as
when the blood is diffused in and colours serous infiltrations, &c.
Few systems in the living economy are furnished with a greater number
of exhalants; I do not speak of those that contribute to its nutrition
and that are consequently found there as in all other organs. The
superabundance of these vessels is owing to the continual exhalation
that is going on there. It is this superabundance which renders, as
we shall see, inflammation so much more frequent in a part where the
cellular texture is in the greatest abundance; it is this that exposes
it to that variety of alterations, in which its texture, loaded with
the different substances it exhales, has a firm appearance, and offers
at one time a fatty substance, at another a gelatinous one, sometimes a
species of scirrhus, &c. &c.
_Absorbents._
The absorbents correspond with the exhalants in the cellular system;
the eye cannot trace them, injections would not reach them. But their
existence there is proved, 1st. by the natural and constant absorption
of fat and serum; 2d. by the more manifest one that produces resolution
of serous infiltrations in dropsies, sanguineous in ecchymosis,
purulent in the different kinds of abscesses that are removed; 3d.
by the disappearance of mild fluids injected into these cells, an
effect that must be owing to the agency of these vessels; 4th. by the
resolution of natural and artificial emphysema, in which the air, or at
least the principles that constitute it, have no other way of escaping.
This is evident when the emphysema arises from a rupture of a bronchial
cell, and when a very little opening is made in the animal, it is
stopped after the air is driven by it into the sub-cutaneous texture;
this I have convinced myself of. 5th. The drying up of external ulcers
is owing to the cellular absorbents. Oftentimes in phthisis the ulcers
are suddenly emptied, and we find in the subject who dies immediately,
only the place that was occupied by pus or sanies; I have already
known two patients to die in this way by a re-absorption almost
instantaneous and exactly analogous to that of external ulcers. 6th.
Where there is the most cellular texture, we meet with the greatest
number of absorbents, and the most of those bodies with a glandular
appearance, in which these vessels ramify. Where the cellular texture
is scarcely discoverable, as in the brain, we can with difficulty see
the absorbent system, &c.
We must consider, then, the cellular system as the principal origin of
the absorbents, of those especially which serve to carry the lymph.
These vessels and the exhalants appear to contribute particularly
to the formation of its structure. Many have thought that it was
exclusively formed of them; but this is not founded either upon
observation or dissection. We see a transparent filamentous texture,
and nothing more. Each cell is a reservoir intermediate between the
exhalants that terminate and the absorbents that arise there. They are
in a small way what the serous sacs are in a large one. We do not see
the orifice of either set of vessels.
_Nerves._
We see many nerves running through the cellular texture. But do these
filaments stop there? Dissection affords no light upon the subject; it
arises perhaps from this, that these filaments being white like the
texture, we cannot see them at their termination as well as we can the
arterial branches, which are rendered apparent by their colour, when
they contain red blood.
ARTICLE FIFTH.
PROPERTIES OF THE CELLULAR SYSTEM.
I. _Properties of texture._
The properties of texture are strongly characterized in the cellular
system.
_Extensibility._
Extensibility is proved in a variety of cases, as in œdema, in the
accumulation of fat, and in different tumours, in which the cells are
much spread and the membranes remarkably elongated. All the natural
motions suppose this extensibility; the arm cannot be raised without
the texture of the axilla acquiring an extent double, or even treble,
what it has when the arm is down. The flexion and extension of the
thigh, of the neck, and of almost all the parts, exhibit in different
degrees analogous phenomena. If we raise any organ from those to which
it is contiguous, the intermediate texture is considerably elongated.
The degrees of the extensibility of the cellular texture vary. In the
sub-cutaneous, the sub-serous, the intermuscular, &c. this property
has much more extended limits than in the sub-mucous layer, in that
exterior to the arteries, the veins, and the excretories. It exists,
however, in this, as is proved by the dilatations of the gastric
viscera, aneurisms, varices, &c. But these phenomena themselves prove
the greater difficulty of extension in this species of texture; for
example, the ordinary texture would be incapable of resisting the
impulse of the blood after the rupture of the coats of the artery.
There would be a sudden, enormous, and often fatal dilatation, if the
arteries were only surrounded by this. It is the thickness of that
which covers them, which makes the progress of these tumours slow and
gradual.
It is in fact an essential character of the extensibility of almost all
the cellular system in which the layers and consequently the cells are
united, to have the power always of being put suddenly in action and in
an instantaneous manner. We have an example of this kind of extension
in emphysemas artificially produced, which make this texture go
suddenly from a state of perfect contraction to the greatest extension
of which it is capable. The artificial injection of different fluids
exhibits the same phenomenon. We observe it also as a consequence of
fractures, and contusions of the limbs, in which we sometimes see
enormous swellings appear in a manner almost as sudden. The cellular
texture is evidently the seat of those swellings which take place in
that texture which is sub-cutaneous, and not in that subjacent to the
aponeuroses, because the extensibility of these membranes not being
capable of being suddenly put into action, resists all dilatation
that is not gradually made. Many other organs, as the tendons, the
cartilages, the bones, &c. though possessing, like the cellular
texture, extensibility of texture, differ from it like the aponeuroses,
in the impossibility of being suddenly distended. In general, the
softness of the primitive structure appears to have great influence
upon this modification of extensibility.
The cellular texture, extended too far, becomes at first very thin, and
then breaks. In a natural state, no motion of the economy is capable
of being carried so far as to occasion this; for example, I have
remarked in regard to cellular texture taken from the axilla, that it
is necessary to extend it at least three times as far as it is in the
elevation of the arm, to produce this phenomenon. Besides, what opposes
also this rupture, is a kind of locomotion of which it is capable; so
that if too violently drawn, it displaces that which is contiguous
to it, draws it towards itself, and thus becomes less stretched. We
see this phenomenon in a remarkable manner in the swellings of the
testicle, in large hydrocele. Then all the surrounding texture, that of
the lower part of the abdomen, the top of the thighs, and the perinæum,
drawn by that which immediately covers the tumour, is thus brought also
upon it.
I have observed that the inflamed cellular texture loses in part this
property, and that upon the dead body it breaks with great ease. This
takes place also in different indurations of which it is the seat. For
example, that surrounding a cancerous womb, being swelled, loses the
capacity of being extended; it is brittle, if I may be allowed to use
the word; the least effort is sufficient to break it. This fact is
uniform in all cancerous affections, somewhat advanced, of the womb and
in those of many other organs.
_Contractility._
Contractility of texture always takes place in the cellular system when
extension ceases. Thus in emaciation, in the resolution of dropsy and
of tumours, the cells contract and lose a great part of the capacity
they had acquired; in a wound which has affected the cellular texture
as well as the skin, the edges separate, and a space remains between
them owing to the contraction of the cells.
As we advance in life, this contractility takes place with less ease;
youth is the period of its greatest energy; thus in consequence of
great emaciation that takes place in old men, the skin is flaccid and
wrinkled, because the subjacent cellular texture not having contracted,
the cutaneous covering remains at some distance from the external
organs and cannot lie close to them. In a young man, on the contrary,
who has become emaciated, the skin is exactly applied to the organs,
it preserves its tension; because the cells in contracting draw it with
them; these form the external prominences. It is necessary to observe
these prominences; in the face, with the folds of the skin, they form
what are called prominent features.
II. _Vital Properties._
The animal properties are not among the attributes of the cellular
texture in an ordinary state; we can with impunity cut it, draw it in
different directions or distend it with gas. An animal that undergoes
these experiments gives no indication of suffering. If he feels any
pain, it is from the nervous filaments that pass through the texture,
and which may be accidentally irritated. In disease however, the
sensibility is raised to such a point, that it may become the seat of
acute pain; phlegmon is a proof of this.
The organic properties are very distinct in the cellular texture;
fat and serum could not be absorbed there, if they did not make an
impression that brings into action organic sensibility. I would observe
concerning this property considered in the cellular system, that all
substances have not an equal relation to it; among the animal fluids
the blood, the lymph and milk do not raise it so high, when they are
effused or injected there, as to prevent absorption, which takes
place of them as well as of fat and serum. On the other hand this
sensibility is so altered by the contact of urine, bile, saliva or
other fluids destined to be thrown out, that inflammation is often the
consequence, and prevents absorption. Among the foreign fluids injected
water is absorbed. Wine and almost all other irritating fluids excite
suppuration, and are thrown out with the pus that arises from them. We
know that in the operation for hydrocele, abscesses in the scrotum are
always the consequence of an accidental passage of the injection into
the cellular texture. Experiments upon living animals agree perfectly
with this fact; every other irritating fluid, diluted acids, alkaline
solutions, &c. produce the same phenomenon.
Insensible organic contractility is clearly proved in the cellular
texture, by the exhalation and absorption that take place there.
It has to a certain extent sensible organic contractility. We know
that cold alone is sufficient to contract the scrotum in a remarkable
manner; that as it is irritated or not, this part has various degrees
of contraction and relaxation; now it appears to contain under the
skin only cellular texture; the filaments of which, it is true, have
a particular appearance and seem to differ in their nature from the
filaments of the other portions of this system. This contraction to be
sure is not to be compared to that of the muscles, but it is certainly
the first degree of it; it is of the same nature, or rather it is a
medium between this and those oscillations that cannot be described,
which we designate under the name of insensible organic contractility,
and others call tone.
_Sympathies._
The relations of the cellular with the other systems are very numerous
and multiplied; but oftentimes it is not easy to perceive them clearly.
In fact, as it is disseminated in all the organs and contributes to
the structure of all, it is frequently difficult to distinguish what
belongs to it, from that which is an attribute of the parts where
it is found. These relations however, become evident under various
circumstances; in acute as well as chronic diseases, it is very
susceptible of the influence of the affections of the organs. I do not
here mean the alterations arising from juxta-position and continuity,
alterations so common as we have seen, but those produced in parts of
the cellular texture that have not any known relation to the affected
organ.
In acute diseases which have their seat in a particular organ, as in
the lungs, the stomach, the intestines, &c. the cellular texture is
often sympathetically affected; it becomes inflamed, suppurates, &c.
Most critical deposits arise from this real though unknown connexion
between the affected organ and the cellular texture. Oftentimes it is
the natural exhalation or absorption of this texture that is deranged
in acute affections; hence the swelling, and dropsies that sometimes
suddenly arise. I attended a man in the ward Saint Charles who, in
consequence of great terror, had a sudden contraction of the epigastric
region; a tinge of the jaundice, an indication of the affection of the
liver by the emotion of the mind, spread in a few hours after over his
face. In the evening he had great œdema of the lower limbs, an œdema
produced, without doubt, sympathetically by the influence of the liver
upon the cellular texture. This influence of the principal organs upon
this system becomes especially remarkable in chronic affections, in
the alterations of texture they experience. We know that most of the
gradual diseases of the heart, the lungs, the spleen, the stomach, the
liver, the womb, &c. have among their symptoms, in the latter stages, a
dropsy more or less general, which arises from the debility created in
the cellular texture. Medicine owes much to Corvisart, for being among
the first to perceive that almost all infiltrations are symptomatic,
that almost all consequently depend upon an influence produced by the
affected organ upon the cellular texture. That comes on gradually then,
which took place suddenly in the patient I mentioned just now.
We see in all acute diseases, that the skin very easily perceives
the sympathetic influence of diseased organs, that it is many times
alternately dry or moist, oftentimes in the same day. I am convinced
that the cellular texture experiences the same alterations as the skin,
and that if we could see what is going on there, we should perceive
that its cells are more or less moist, or more or less dry, according
to the kind of influence it receives; it is to this also that must
be referred the different state of bodies that have died of acute
diseases, which present innumerable varieties in their cellular serum.
Most physicians consider in too general a manner a number of symptoms,
which, to speak correctly, do not depend as they imagine, upon the
disease, but wholly upon a sympathetic affection produced by the
diseased organ upon the sound ones, which, according as they are
affected, give rise to different phenomena truly foreign to the
disease, that sometimes render it complicated but do not form an
essential part of it; they can take place or not, and the disease
remains the same.
Observe that organic sensibility and contractility are almost always
in action in cellular sympathies, because these are the two vital
forces essentially predominant in that system. Thus sensible organic
contractility and animal contractility are particularly exercised in
muscular sympathies, according as the system of organic muscles, or
that of the muscles of animal life, receive sympathetic excitement.
The cellular system not only receives the influence of other organs
in its sympathies, but it exercises its own upon them. In phlegmon,
which is the inflammatory state of this system, if the tumour is
considerable, different alterations are oftentimes discoverable in
the functions of the brain, the heart, the liver, the stomach, &c.
Sympathetic vomiting, which is called an overflow of bile, delirium,
&c. are phenomena that are seen with large phlegmonous swellings
without belonging to the disease itself. Art avails itself of the
influence of the diseased cellular system upon other organs, in the
introduction of setons. Oftentimes in diseases of the eyes, a seton
produces an effect that cannot be obtained from a blister: why? because
the relation that exists between the cellular texture and the eye, is
more active than that which unites the latter to the integuments.
_Characters of the vital properties._
After what has been said, we see that the vital activity is
sufficiently evident in the cellular system. In this point of view,
it is much superior to other organs that are white like it, and among
which it has been ranked, such as the aponeuroses, the tendons, the
cartilages, the ligaments, &c., organs remarkable for the obscurity
of their vital forces and the dullness of their functions. Thus the
phenomena of inflammation go through their different periods much
quicker in this system. Their progress is very rapid, compared to that
of different tumours that appear in the systems of which I have just
spoken.
Suppuration takes place here with a rapidity of which we have an
example in but few of the organs. Every one knows the fluid that comes
from this suppuration. Its colour, its consistence, all its external
qualities have become the type to which we refer the ideas that we form
of pus; so that that which does not resemble it, is considered to be
pus of a bad kind, or as we say sanious. This opinion is incorrect.
Certainly the pus that flows from a bone, a muscle, the skin in
erisypelas, the mucous membranes in catarrh, is of a good kind so long
as the inflammation is regularly going through its periods; it is
however totally different from cellular pus. As this is most frequently
observed, especially in surgery, we have formed a general idea of
laudable, as of sanious pus. Cutaneous, mucous, osseous pus, &c. have
each their peculiar sanies, which differs among them according to the
vital alterations of the organ, from which it is derived. So that the
pus of each system differs from that of the others, in the same way as
the alterations of which it is susceptible are different from their
purulent alterations.
Has the cellular texture peculiar vital modifications in those organs
to whose structure it contributes? From what has been said above, it
seems hardly probable. All that I have been saying, applies to the
system considered in the interstices of the organs, separate from all
combination with their structure. It is possible however that its vital
activity is diminished in the cartilages, the tendons, &c., that it is
increased a little in the skin, that its life, in general tends to an
equilibrium with that of the parts in which it is found; but these are
conjectures that nothing positive confirms.
That which ought not to escape us here, is the manifest difference
of vitality that exists between the texture of layers and filaments
almost every where spread, and the texture that is wholly filamentous,
which is exterior to the mucous surfaces, to the blood-vessels,
and excretories, a difference from which arises the rareness of
inflammation and tumours in this last. It is often a real barrier that
stops the affections of the first, a barrier that protects the organ
it covers. Thus I have many times observed in opening bodies, that
whilst the ordinary texture, in which the arteries are embedded as in
the axilla, is in a state of suppuration, and almost disorganized by
the pus, that which forms the external covering of the vessels remains
untouched; it has not undergone the least alteration. I have seen the
same phenomenon in the texture exterior to the urethra in deposits of
pus at the loins.
III. _Properties of re-production._
The cellular texture is distinguished from other organs by the
faculty it has of throwing out a kind of vegetation, of elongating
and re-producing itself, of growing when it has been cut or divided
in any manner. It is upon this faculty that depends the formation of
cicatrices, tumours, cysts, &c.
_Influence of the cellular texture upon the formation of cicatrices._
Cicatrices may be considered under two relations, 1st. in the external
organs, in the sub-cutaneous texture and skin particularly; 2d. in the
internal organs. Let us examine them at first in the external.
Every wound that follows the ordinary periods, presents between its
formation and its cicatrization, the following phenomena; 1st. it
inflames; 2d. fleshy granulations are formed upon its surface; 3d.
it suppurates; 4th. it sinks down; 5th. it is covered with a fine
pellicle, red at first and afterwards becoming whitish. Let us trace
these different periods.
_First period._
Inflammation commences the instant the wound is made. This is the
sudden result of the irritation caused by the instrument, the contact
of the air, the dressings and surrounding bodies. Shut out until
then from the contact of the air, most of the parts concerned in the
solution of continuity, enjoy only organic sensibility; but then these
contributing to form the surface of the body, ought to enjoy animal
sensibility, that which transmits to the brain the impressions that
are received. Now the effect of inflammation upon organs endowed only
with the first kind of sensibility, is to raise it so much, that it
ascends to the same degree as the second, and can like it, transmit to
the brain its impressions; so that by it the parts divided by a wound
become capable of performing the functions of the integuments. This
is the first advantage, without doubt, of this inflammatory period of
cicatrization.
Another advantage of this period is to dispose the parts to the
development of fleshy granulations. In fact, inflammation always
precedes this development; now the increase of life that it produces
in the organs, appears to be necessary to animate the parts that are
to be reproduced; by it the cellular texture, where the granulations
are formed, is endowed with more sensibility and more insensible
contractility; it raises it to a temperature above that of the
neighbouring organs; it becomes the centre of a small circulating
system independent of that of the heart. It is in the midst of
this extension of the forces, that the fleshy granulations arise
and increase, for the production of which the natural forces would
have been insufficient. Hence the paleness and flaccidity of these
granulations, when these different functions are weakened or cease.
_Second period._
The production of fleshy granulations succeeds to inflammation. It
presents the following phenomena; small reddish bodies, like tubercles,
arise, unequal and irregularly disposed upon the surface of the wound;
they are not fleshy, as their name, given, no doubt, on account of
their colour, would indicate; they are little cellular vesicles, filled
with a thick substance, like lard, which we are unacquainted with, and
which it is important to analyze. This substance so fills the cells,
that in blowing air into the texture subjacent to a wound, whether in a
living or dead body, this fluid does not enter the granulations; they
are raised up entire, but no one of them is developed or distended as
the cells which this substance does not fill; the granulations remain
the same in the midst of the general bloating. I have often made these
experiments upon animals that I have wounded for the purpose.
In proportion as the granulations are developed upon an exposed
cellular surface, we see them unite together, and form, by their
union, a kind of provisional membrane, which absolutely prevents the
contact of air upon the subjacent organs, while the true cicatrix,
that which is to be permanent, is forming. This provisional membrane
of cicatrices, this kind of epidermis destined to defend the parts
during the work of cicatrization, differs from common serous membranes
in this, that they are smooth and every where uniform, whilst the
granulations produce here an unequal and rough surface. This inequality
of the granulations and their separation, appear to be opposed to what
I have said concerning the first state of cicatrices; the following
experiment leaves no doubt upon the subject. I made a large wound
upon a dog, and let it go through its first periods; the animal was
then killed. I removed a portion of flesh upon which the granulations
were developed; I distended it by a prominent body, placed on the
side opposite to the granulations, so as to make the granulated
surface convex, that had been concave; the tubercles were effaced; the
provisional pellicle, stretched out, became very evident; it might have
been taken for an inflamed serous membrane.
It follows hence, that when the granulations are united together, that
the air is entirely excluded, and that what is commonly said of the
contact of this fluid is inaccurate and contrary to the arrangements
of nature, which knows how better than we can do by our dressings, to
cover over a divided part, whilst the work of cicatrization is prepared
and effected.
These are the general phenomena that cutaneous cicatrices offer in
the two first periods of their formation. The internal cicatrices
show nearly the same thing. Now it is easy to prove that the cellular
system here performs not only an important but an exclusive part, and
that all these phenomena take place in its texture or its cells. The
following observations prove in a satisfactory manner the cellular
nature of the granulations and the provisional pellicle that arises
from them. 1st. Where the cellular system is most abundant, as in the
cheeks, granulations grow most easily and wounds are soonest healed.
2d. The skin, stripped too much of the cellular texture, is not
covered with ease with these productions, and adheres with difficulty
to the neighbouring parts; hence the precept so strongly inculcated
in surgery, of saving this texture in dissecting out tumours, in the
extirpation of wens, cysts, &c. 3d. Maceration always reduces to
this first base the surfaces of granulating wounds, when we expose a
dead body that has one to this simple experiment. 4th. The nature of
fleshy granulations is the same every where, whatever be the organ
that produces them, whether a muscle, a cartilage, the skin, a bone, a
ligament, &c.; only they are more or less backward, according as the
life of each organ is more or less active, more or less decided, and
the vital forces found there marked in a greater or less degree; thus
they appear at the end of four or five days upon the skin, and it is
very much longer before they are visible upon the bones; but their
structure, their external appearance, their nature, are always the
same; then they are only the expansion, the enlargement of an organ,
that is met with in all the others; now this organ common to all, this
general base of every organized part, is the cellular texture.
From the red colour of fleshy granulations, it has been thought that
they were a vascular expansion; but their development is unlike every
production of the blood-vessels. On the one hand we have seen, that
the cellular texture contains so many exhalants and absorbents, that
it seems to be almost made up of them; on the other hand, we shall see
that in inflammation a passage is constantly given to red blood in this
kind of vessels; then, as the fleshy granulations are cellular, they
consequently partake of the nature of this system; and when found in
a real inflammatory state, we conceive that their redness is the same
as that of an inflamed pleura, of the cellular texture that has become
the seat of phlegmon, of erisypelatous skin, &c.; a redness that does
not imply an elongation of blood vessels, but only the passage of red
blood, in those that usually carry white. This is so true, that when
the inflammation is gone, the blood ceasing to enter these vessels, the
membrane takes its natural colour; so that the granulations, after the
formation of the cicatrix that arises from their near approach to each
other, whiten because the blood no longer enters them. Now if it had
been a new production of vessels, they would continue and perform their
functions. Moreover, how can we suppose a development of blood-vessels
where they did not primarily exist, as in the tendons, the cartilages,
&c. which have, like other organs, fleshy granulations in their
solutions of continuity?
Let us conclude from these circumstances, that the arterial system
is not connected with the formation of fleshy granulations; that the
cellular system is alone concerned in it, because that this alone is
endowed with the faculty of increasing, extending, and reproducing
itself.
This is what takes place in the second period of the cicatrization of
wounds; the cellular texture, by the increase of power that it acquired
in the first period, is raised into vesicles irregularly disposed,
which exhale a white substance, that is not well understood, and unite
at their superficies and form a provisional membrane. But how is this
membrane changed into that of the cicatrix? Observe nature, and you
will see that it brings on suppuration and a sinking down of the parts,
before the arrival of this period.
_Third period._
The period of suppuration does not take place in the cicatrization of
the bones, in that of broken cartilages, of torn muscles and generally
in the reunion of all divided organs without external wounds. We must
then show what relation there is between their cicatrices and those
of the external organs; for a common principle presides over all the
operations of nature, though they may have a different appearance.
When a bone is broken, the two first periods of its reunion are the
same as those of the external organs; the ends inflame, and then
are covered with cellular granulations. In the third period, these
granulations, having first united together, become a kind of secretory
or rather exhalant organ, which separates first the gelatine which
encrusts it, and gives to the callus a cartilaginous nature, and then
the phosphate of lime which completes the osseous arrangement. In the
cicatrization of cartilages, gelatine only is exhaled; in that of the
divided muscles, fibrin, &c.; in a word the cellular texture is the
common base of all the cicatrices of the internal organs, then the
fleshy granulations are the same for all; they resemble each other
in each having the same base; that which establishes the difference
between them, is the substance that is separated, and which remains
in the cellular texture. This substance is generally the same as that
which serves for the nutrition of the organ, and which is by this
function, constantly carried there and brought away. Now as each organ
of the different systems has its peculiar nutritive substance, each has
its peculiar mode of reunion; we should understand the cicatrization of
the different organs, as well as that of the bones, if the substances
that nourish these organs were as well known as gelatine and phosphate
of lime. The mode of development of the internal cicatrices is in
general analogous to that of nutrition, or rather it is the same with
this difference only, that the cellular texture rising into irregular
granulations upon the divided surfaces, does not afford to the cicatrix
a base formed upon the shape of the organ; hence the inequality of
callus, &c.
This then is what in general takes place in the third period of the
cicatrization of the internal organs: phenomena very analogous are
seen in that of the external. The membrane which covers the fleshy
granulations thus becomes a kind of exhalant organ which separates
from the blood a whitish fluid that is called pus. But there is
this difference, that instead of remaining in the texture of the
granulations, of penetrating and encrusting it, as the phosphate of
lime and gelatine penetrate the bone, it is thrown out and has nothing
to do with the reunion; so that in internal cicatrization there
is exhalation, then incrustation of the exhaled fluid, and in the
external, there is exhalation and then excretion of this fluid.
Besides, an internal wound which affects the cellular texture and
suppurates, appears to me to resemble perfectly serous surfaces, which
are covered in consequence of their inflammation with a purulent
exudation. The fine pellicle that covers the granulations is of the
same nature as an inflamed pleura or peritoneum, that is, it is
essentially cellular. The pus is in both cases almost of the same
nature, and analogous to that of phlegmon, because it comes from
similar organs, whilst if the skin alone is concerned, this fluid is of
a very different nature, as we see in erisypelas.
The exhalation of pus upon a cicatrizing surface and serous membranes,
appears to me to have a great analogy with the whitish substance of
some kinds of cysts.
_Fourth period._
Suppuration gradually exhausts the whitish substance that fills the
granulations; then their cells, which were at first swelled, insensibly
diminish in size, they close by their contractility of texture; by
degrees they adhere to each other, and from their adherence arise the
following phenomena. 1st. All the fleshy tubercles disappear and there
is a uniform surface in their place. 2d. This surface is a very fine
membrane, because the thickness of the granulations arose not from the
cells, but the substance they contained, and which being taken away,
leaves them empty. 3d. This membrane has infinitely less width than
the pellicle that first covered the granulations, because the cells in
contracting, draw the edges of the cicatrix from the circumference to
the centre; these approximate, and the breadth of the wound diminishes;
the same granulations that in the beginning occupied a space of half a
foot diameter, as for example in the operation for cancer, are often
contracted to an inch or two.
When the adhesion is complete between all the cells that first form
the fleshy granulations, the membrane of the cicatrix, the result of
this adhesion, exists. Thus it is that all the flesh, the development
of which astonishes us, and which amply repairs the loss of substance,
is but a pellicle, reddish when the exhalants are full of blood, but
afterwards white by the return of this blood into its vessels.
From this mode of origin of external cicatrices, it is easy to
conceive, 1st. why they adhere intimately to the places in which they
are found, and have no laxity in the integuments; 2d. why the skin
approximates from all the neighbouring parts to cover the wound; 3d.
why it wrinkles in approximating; 4th. why, where it yields the most,
the cicatrix is the smallest, as in the scrotum, the axilla, &c.; and
why on the contrary it is the largest, where it yields but little,
as on the sternum, the cranium, the great trochanter, &c.; 5th. why
the thickness of all cicatrices is uniformly in an inverse ratio to
their width; in fact as there is only the same quantity of cellular
granulations to form them, it is necessary that they should lose in
one way what they gain in another; hence those that are broad are
much more easily torn; 6th. why they have not a regular organization,
do not partake of the functions of the cutaneous organ they replace,
and why their texture is absolutely different from this organ. The
cicatrization of wounds left to themselves, especially those with
loss of substance, differs essentially from the union by the first
intention, which is effected by the agglutination of the edges. In this
last there is neither the second period, that of fleshy granulations,
nor the third, that of suppuration, nor the fourth, that of sinking
down. Union succeeds immediately to the first, that of inflammation.
We see, from all that has been said, that the cellular texture is the
essential agent in the production of all cicatrices, that it forms
their basis and their principle, that without it they could not take
place, and that they depend especially upon the property it has of
extending and increasing.
_Influence of the cellular texture in the formation of tumours._
In the formation of cicatrices, the cellular texture grows but a few
lines above the level of the place of division; the cells it forms in
its reproduction are generally small. It is not so when there is a
departure from the ordinary laws of cicatrization, when any accidental
cause alters the vital properties; then we see a very extensive growth,
which often has more of this texture than the parts from which it
arises. All those different excresences, known by the names of fungous
flesh, fleshy protuberances, soft flesh, &c. are but the result of this
increase of the cellular system, being greater than what it should be
by the ordinary laws of cicatrization; thus the cicatrices are not
effected while these irregular productions continue; it is not until
they are repressed that consolidation takes place. But it is especially
in different tumours that we see this development, this remarkable
growth of cellular texture. All the fungi, and productions that are
developed exclusively in the mucous membranes, in the sinuses, the
nasal cavities, the mouth and the womb particularly, and which differ
essentially from those that have their seat on the fibrous membranes,
the dura-mater for example, though they are compounded under a common
name, all the fungi, I say, arise from the cellular texture, they are
of a peculiar substance deposited there, which as it is more or less
abundantly separated, leaves its primitive base more or less exposed.
Polypi, whether mucous or sarcomatous, tumours that are equally the
attribute of the mucous system, have also the cellular texture for
the primitive base of their organization. All the different kinds of
cancers exhibit it in a manner more or less evident, in the swelling of
the parts which they occasion. It would be necessary to notice almost
all tumours, to point out those that the cellular texture assists to
form.
We may then consider it as forming the general base, the nutritive
parenchyma of almost all excrescences. It shoots up, and grows first
at the part where the tumour is to be developed; then it is encrusted
with different foreign substances, and their difference constitutes
the difference of the tumours. These phenomena are precisely analogous
to those of ordinary nutrition. In fact, all the organs resemble each
other in their nutritive base, the parenchyma of nutrition, which
is vascular and cellular; they differ in the nutritive substances
deposited in this parenchyma. All tumours then are cellular, this
is their common character. Their peculiar character is derived from
the substances that the texture separates, according as the morbid
alterations of which it is the seat, modify differently its vital
forces and place it in relation with this or that substance; thus as we
have said, all the internal cicatrices are similar in the first period,
in that of fleshy granulations, and differ as the nutritive substance
of the organ to which they belong, penetrates them.
Thus we see, that nature is the same in her operations, that a
uniform law presides over all, and the only difference arises from
the application of this law. Wherever there is natural nutrition or
an accidental modification of this function, the cellular texture
performs an essential part; now this important part which it has in
cicatrization and the formation of tumours, arises from the singular
property it possesses of extending itself, of dilating and growing.
Examine the tumours that appear in the muscles, the tendons, the
cartilages, &c. you will not see there an expansion of fleshy, or
tendinous fibres, or of the cartilaginous substance, &c. the cellular
texture alone goes from the organ and is spread in the tumour; thus
the fibres of the bones, the muscles, the fibrous substances divided
in solutions of continuity, are not raised above the level of the
wound, as the cellular texture of the part is for the production of
granulations.
The tumours of which I have spoken, have nothing in common, as has
been imagined, with the acute swellings that constitute phlegmon,
nor with that engorgement that the limbs experience where there is a
violent irritation, as a compound fracture or luxation, a whitlow, a
puncture with a poisoned weapon, &c. an engorgement that is generally
seen around the whole external parts, which are violently affected;
it sometimes comes on almost instantaneously, and is not really
inflammatory, though there is tension, pain, &c.; it deserves rather
the name of inflation than engorgement.
We must not confound these tumours with certain chronic swellings,
in which, without increasing or growing, the cellular texture is
infiltrated, and different substances enter it, that change its nature;
such are those that take place in the diseases of the articulations;
such is the callosity of fistulas, &c.; the fatty matter that is found
in some tumours, &c. In all these cases there is neither growth or
enlargement, as in a polypus, a fungus, &c.; it is a substance more
solid than serum, that infiltrates the cellular texture, obliterates
its layers, and presents a homogeneous appearance.
There is after death a great difference between an acute and chronic
tumour, between that produced by growth and that by infiltration.
In fact, one remains the same, and preserves, until putrefaction,
its size, its form, and its density, like all the organs. The other
sinks away, as I have remarked, by the loss of the vital forces. This
subsidence varies; if the tumour is nothing but the cellular inflation
of which I have spoken, and which is so common in external injuries,
it entirely disappears; if, besides this inflation, there is an
accumulation of blood, as in carbuncle, phlegmon, &c. a portion of the
tumour remains, though always much diminished in size. It is generally
in this inflation, of the immediate cause of which I am ignorant, that
the subsidence especially takes place. Let us pass to a function of the
cellular texture not less important, and which is very analogous to
this.
_Influence of the cellular texture in the formation of cysts._
A cyst is a membrane, in the form of a sac without an opening, which
is accidentally developed, and which, containing fluids of a different
nature, has been on this account divided into many species. The cysts
are formed from the cellular texture; they arise in its cells, grow in
the midst of them, and have all its characteristics.
To be convinced of the influence of the cellular system in the
formation of cysts, it is sufficient to prove that between them and the
serous membranes, there is the greatest analogy, and almost identity;
for we shall see that these membranes are essentially cellular. The
following are some of the analogies of these two kinds of productions,
the one of which is natural and the other accidental.
1. Analogy of conformation. The cysts form all kinds of sacs without an
opening, containing a fluid that is exhaled from them, having a smooth,
polished surface contiguous to this fluid, an uneven, loose one,
continuous with the neighbouring cellular texture.
2. Analogy of structure. Always formed of a single layer, like serous
membranes, cysts have like them a cellular texture, as is proved
by maceration and inflation. Thus they constantly arise in the
midst of the cellular organ, usually where it is most abundant. Few
blood-vessels enter them; the exhalant system is conspicuous there.
3. Analogy of the vital properties. There is no animal sensibility in
them in an ordinary state, but it is very evident in inflammation;
organic sensibility is always remarkable in them, and tone, which is
characterized by a slow and gradual contraction, in consequence of the
artificial or natural evacuation of the contained fluids, &c.; these
are the characters of cysts, they are also, as we have seen, those of
serous membranes.
4. Analogy of functions. Cysts are evidently secretory or rather
exhalant organs, which exhale the fluid they contain. Exhalation
becomes very evident there, when after the evacuation of the fluids,
the membranous sac has not been removed, or an artificial inflammation
excited in it. Absorption is proved, in the spontaneous cure of
encysted dropsies, a cure which must depend on this function alone.
5. Analogy of affections. Who does not know that between the dropsy of
the tunica vaginalis and the encysted dropsy of the cord, there is the
greatest analogy; that the curative means are the same, that in both
cases the inflammation that is produced by the injection of a foreign
fluid, wine, for example, is the same, and that the cure is effected
by a similar mechanism? Whoever has opened two bodies, each having
one of these affections, and examined the sacs in which the fluid is
contained, must have perceived that their appearance is precisely the
same. Remove the fluid from the cyst of a soft wen, and you will
discover but little difference between it, dropsical cysts, and serous
membranes.
The preceding considerations induce us to admit a perfect resemblance
between cysts and serous membranes, of whose characters they partake,
and into the system of which they essentially enter, and consequently
into the cellular system. It is very probable that there is a relation
between them, and that when a cyst is formed and exhales copiously,
the exhalation of the serous membranes is diminished; this does not,
however, rest upon direct proof. There is this essential question,
how are these cysts developed? How a membrane, which does not
exist in a natural state, can arise, grow, and even acquire a very
considerable development under certain circumstances. This problem
is usually resolved in the following manner; at first, it is said,
a small quantity of fluid collects in a cell; this fluid increases
and dilates in every direction, the parietes of the cell, which are
attached to the neighbouring cells and thus increased in thickness.
Gradually this fluid, serous in dropsy, white and thick in steatoma,
&c. increases in quantity, presses in every direction the sac that
contains it, enlarges, crowds against the neighbouring organs, and
thus acquires the form under which we see it. Nothing at first sight
appears more simple than this mechanical explanation; nothing is less
conformable to the process of nature. The following considerations
will serve to prove this. 1st. The cysts are analogous in every point
of view to serous membranes; how then could they have a different
origin from these membranes, which are never formed, as we shall see,
by the compression of the cellular texture? 2d. Does an origin thus
mechanical, in which the vessels compressed against each other would
inevitably be obliterated, as we see the skin become callous, accord
with the exhaling and absorbing function of the cysts and with their
peculiar kind of inflammation? 3d. Why, if the cells adhering to each
other, form these unnatural sacs, is not the neighbouring cellular
texture diminished and destroyed, even when they acquire great size?
4th. If, on the one hand, the cysts are formed by the compression of
the cellular texture, and if it is true on the other, as we cannot
doubt, that their fluid is exhaled by them, it is necessary to conclude
then, that this fluid pre-exists in the organ that separates it from
the blood: I would as soon assert that the saliva pre-existed in the
parotid, &c.
The immediate consequence of the preceding reflections, I think, is,
that the common explanation of the formation of cysts, is directly
opposite to the general course that nature pursues in her operations.
How, then, do these sacs arise and grow? these tumours that appear
externally, or are developed within; for there is no difference in
these two sorts of unnatural productions, except in the form. Most
tumours throw from their external surface the fluid that is separated
there. A cyst, on the contrary, exhales this fluid by its internal
surface, and preserves it in its cavity. Suppose a fungous, suppurating
tumour, suddenly becomes a cavity, and suppuration is carried from the
external surface to the walls of this cavity; this will be a cyst.
On the other hand, suppose a superficial cyst, the cavity of which
is obliterated, and the fluid of which is exhaled upon the external
surface; this will be then a suppurating tumour.
As the form, then, establishes the only difference between tumours and
cysts, why should not the formation of one be analogous to that of
the other? Surely, no one ever thought of attributing to compression,
the formation of external or internal tumours. We may conceive of the
production of cysts in the following way; they begin to be developed
and grow in the midst of the cellular organ, by laws very analogous
to those of the general increase of our organs, and which seem to be
aberrations, and unnatural applications of these fundamental laws, of
which we are ignorant. When the cyst is once characterized, exhalation
commences; at first scanty, it afterwards increases as the cyst
grows. The increase of the exhalant organ, then, always precedes the
accumulation of the exhaled fluid, so that other things being equal,
the quantity of suppuration in a tumour is in a direct ratio to its
size.
ARTICLE SIXTH.
DEVELOPMENT OF THE CELLULAR TEXTURE.
I. _State of the cellular system in the first age._
In the first periods after conception, the fœtus is only a mucous mass,
homogeneous in appearance, and in which the cellular texture seems
almost exclusively to predominate. In fact, when the organs begin to
be developed in this mass, the spaces that are left between them are
filled with a substance which, exactly similar to that which before
formed the whole of the body, can be considered as the residue of it,
or rather perhaps it exists in a distinct manner, because it has not
been penetrated with the peculiar nutritive substance, like that which
forms the parenchyma of nutrition of the organs, which before this
penetration resembled it precisely. This substance that lies between
the organs, and which is the principle of the cellular texture, is the
farther removed from a fluid state, as the period of labour approaches.
First it is a true mucus, then a kind of glue, then the cellular
texture begins to appear.
This primitive state of the cellular organ, this appearance that it has
at first, is owing to the great quantity of fluids that enter it at
that period; it does not denote an inorganic existence; we can then
compare it to the vitreous humour, which appears wholly fluid at first
sight, because the transparency of its layers do not permit us to see
them in the humour that enters its cells; make a puncture so as to
evacuate this humour, and they become evident.
Thus the cellular texture, extremely fine and even transparent in the
first periods of life, is then concealed by the humour that fills it,
and becomes more sensible as this humour diminishes with age. This
phenomenon sometimes takes place in after life, in different serous
infiltrations, those especially in which the infiltrated fluid has some
viscidity.
What is this humour that is so abundant in the cellular system, in
the first months after conception? Is it albuminous like that which
afterwards lubricates it? Probably it is; I should think, also, that it
has much of the character of gelatine, a character which predominates,
we know, in the animal humours at this period; I know of no experiment
upon this point. Whatever the humour is, it is much more viscid and
unctuous than it is afterwards; the touch is sufficient to convince us
of this. It is its predominance, joined to the delicacy of the cellular
layers, that, in the first months, makes every attempt to render the
fœtus emphysematous, by blowing air under the skin, almost absolutely
useless.
At birth and some time after, the great quantity of sub-cutaneous fat
makes artificial emphysema very difficult; it does not appear that the
fœtus ever has a natural one. The delicacy of the cellular layers and
filaments is such at this period, that the imagination cannot represent
it; the texture of the hair is gross in comparison with it. I presume
that the ball of fat, which I have said almost always exists in the
cheek of the fœtus, arises from a rupture of several layers, a rupture
from which is produced a great cell, that is filled with fat.
Sometime before birth, at that period and in the subsequent years,
the cellular humour constantly diminishes; the cells become dryer,
consequently more apparent; the whole mass of the cellular system
diminishes, because as the organs increase, the interstices are
contracted. This system however predominates for a long time over the
others; hence the roundness of form that characterizes the infant, the
want of prominence of its organs, that are almost concealed by it;
hence in part the suppleness and multiplicity of its movements; hence
also the frequent diseases of which it is the seat at that age.
The layers still preserve an extreme delicacy; they are still easily
broken. In producing emphysema, upon very lean children, I have
observed that often it forms in places very considerable dilatations,
a kind of sacs in which the air accumulates in large quantity, and
which arises from this rupture; whilst in the same experiment upon
an adult, the air is propagated in an uniform manner and constantly
infiltrates the cells without destroying them. By comparing in our
slaughter-houses, the flesh of calves blown, and that of oxen in the
same state, I have sometimes made an analogous observation.
In infancy and in youth, the vital energy of the cellular texture is
very conspicuous; at this age, the fleshy granulations, essentially
cellular as we have seen, arise more promptly and go through their
periods more rapidly than at any other age; the union of wounds is
easier; and all tumours, have in their development and their progress,
a rapidity that particularly depends upon the high degree to which the
vital forces of the cellular system are raised at this period. It is
to the same cause, that must be referred the facility of absorption of
serous fluid, which sometimes infiltrates accidentally the cells, as we
see in the scrotum, the eye-lids, &c.; the suddenness of the formation
of cysts, &c.; then dropsies are much less frequent. When they do take
place, why are the superior extremities almost as often affected as
the inferior, whilst the leucophlegmasia of adults commences almost
always in the last? This is then as remarkable a phenomenon, as the
singular tendency that there is in the legs of being infiltrated,
compared with the arms. Does not this depend upon situation, which,
forcing the lymph to ascend against its weight, gradually weakens the
absorbents when it has continued for some time? This explains, why
varices are, as we know, more frequent in the inferior than superior
extremities.
II. _State of the cellular system in the after ages._
In the adult, the cellular texture is condensed and becomes firmer;
its layers have a more compact texture. It appears also to lessen
in quantity, because as the organs increase in thickness, their
interstices are contracted. If there is not a real diminution, there
is at least one in comparison with the state of the organs. It is to
this circumstance that must be attributed in part, their prominence
under the integuments, the striking appearance of the form of the
muscles, &c. It appears besides, that the quantity of cellular texture
varies according to temperaments; that in those called phlegmatic or
lymphatic, it predominates over the other systems, and in the bilious,
which is characterized by a dryness and rigidity of fibre, it is in the
smallest proportion. In women, it is in larger quantity than in men;
the roundness of their forms is in part the result of this.
The motion of a part appears to have no effect in producing a more
active nutrition of its cellular texture, as takes place in the
muscles, the nerves, and sometimes even in the blood-vessels.
In old age this texture is condensed and contracted; it acquires
consistence and hardness. The teeth tear it with difficulty in the
boiled flesh of old animals; like it, it is tough and requires long
boiling to soften it. Much less fluid is exhaled there, hence a sort
of dryness and rigidity, that render the motions of old age difficult.
A kind of withering, that it experiences, contributes essentially to
the general diminution that the body then undergoes. It loses its
vital forces; hence its laxity, that prevents it from supporting the
skin as usual. This becomes every where loose, dependent even in some
places, in which it forms folds. The scrotum has no longer the power
of contracting that characterized it and which it derived from the
forces of the cellular system. This general relaxation, this sort of
flaccidity is the constant attendant of old age, in individuals even
in whom excess of all kinds, or a primitive disposition, have rendered
this age premature. I saw at the Medical Society a dwarf, sixteen years
of age, hardly two feet high, who had already begun to grow old; his
sub-cutaneous texture had that laxity, that does not belong to his age.
The premature decrepitude of the dwarf of the king of Poland, exhibited
the same phenomenon. Two persons who lived a long time with him
informed me, that at his death, there was externally this relaxation
and flaccidity of integuments, of which the subjacent cellular texture
appears to be the seat.
It is rare in old age to find osseous incrustations in the cellular
texture. In the great number of old persons that I have had occasion
to dissect, or to have dissected, I remember to have seen but one,
and that occupied the posterior part of the mesentery. I have seen
some others in adults, especially in women, in whom they are found
frequently, in the cellular texture that separates the womb from the
rectum; I have preserved several specimens of these.
NERVOUS SYSTEM OF ANIMAL LIFE.
All anatomists have heretofore considered the nervous system in
an uniform manner; but if we reflect a little upon the forms, the
distribution, the texture, the properties and the uses of the different
branches that compose it, it is easy to see that they should be
referred to two general systems, essentially distinct from each other,
the one having the brain and its dependancies for its principal centre,
and the other, having the ganglions. The first belongs especially to
animal life; it is on the one hand the agent, that transmits to the
brain the external impressions that are to produce sensations; and on
the other it serves as a conductor of the volitions of this organ,
which are executed by the voluntary muscles to which it goes. The
second, almost every where distributed to the organs of digestion,
of circulation, of respiration, of the secretions, belongs more
particularly to organic life, in which it performs a part much more
obscure than that of the preceding one. Neither is strictly confined to
the organs of either life. Thus the cerebral nerves send some branches
to the glands, to the involuntary muscles, &c.; and the nervous system
of the ganglions have ramifications in the voluntary muscles. It is
from the general arrangement, without regard to particular exceptions,
that the division of the two nervous systems is founded, between which
I shall not draw a parallel here to show their difference, because the
description of each will be sufficient to do this.
The nervous system of animal life is exactly symmetrical, like all the
organs of that life. The brain and spinal marrow, which are the double
origin of this system, have this character in a remarkable degree.
Nerves precisely similar go from them; hence the name of pair, by
which is designated the double, corresponding trunk, a name, that we
should not be able to employ commonly in the system of ganglions. There
are then really two nervous systems of animal life, the one right,
the other left; the median line separates them. Their distinction is
apparent not only from dissection, but from their diseases. At one
time exactly one half of the body is deprived of motion, and the whole
nervous system of that side remains passive, the other retaining its
ordinary activity; at another, one side only has an unnatural energy
and becomes the seat of convulsions, while the other remains calm. In
both cases, sometimes the phenomenon is general; often it is limited
to a greater or less number of lateral organs; but always there is an
evident separation between the two nervous systems, the right and left.
The kind of partial paralysis, of which I just spoke, and the principal
character of which arises from the symmetry of the nervous system of
animal life, is wholly different, as it regards this character, from
that in which the lower parts of the body are deprived of motion in
consequence of a fall upon the sacrum, or any other analogous cause.
The relations of size of the nervous system with the brain are in man
and most quadrupeds, in an inverse proportion, as has been observed
by Soemmering. In man the brain is much more voluminous than in
the others, who have nerves larger than his. It is easy to prove
this assertion, in all the animals that we commonly employ for our
experiments; in fact, small dogs are used, on account of the size
of their nerves in very delicate experiments upon sensibility. This
difference is a striking proof of the superiority of man, as it
respects the intellectual phenomena, which are all referable to the
encephalic mass. On the other hand, many animals are superior to him
as it respects motions and the four senses of taste, of smell, of
hearing and seeing. Observe however that he surpasses them all in the
perfection of the fifth sense, viz. that of touch. Why? Because this
sense is entirely different from the others, is consequent to them, and
corrects their errors. We touch, because we have seen, heard, tasted
and smelt. This sense is voluntary; it supposes reflection in the
animal that exercises it, the others do not. Light, sounds, &c. strike
the respective organs without any effort of the animal; but he touches
nothing without a preliminary act of the intellectual functions. It
is not then astonishing, that the perfection of the organs of touch
and the great development of the brain, should be in man, in the same
proportion, and that in those animals, in whom the brain is more
contracted, the touch should be more obtuse and the organs less perfect.
ARTICLE FIRST.
EXTERNAL FORMS OF THE NERVOUS SYSTEM OF ANIMAL LIFE.
I shall consider these forms, 1st. in the origin; 2d. in the course;
3d. in the termination of the cerebral nerves.
I. _Origin of the cerebral nerves._
The word origin should only be understood in relation to anatomical
arrangement. In fact, the nerves are formed at the same time as the
brain; they are rather organs of communication with this viscus, than
elongations of it. If we take a view of the functions of one part of
the nervous system, we shall see that the termination is at the brain,
and the origin is upon the surface. Is it not said that the nerves
go towards this or that part, that the arteries take this course,
wind about, &c.? These are only metaphorical expressions, the least
reflection will determine their meaning.
The nerves of animal life derive their origin from three principal
portions of the encephalic mass; 1st. from the cerebrum; 2d. from the
Tuber Annulare or Pons Varolii and its elongations; 3d. from the spinal
marrow; the cerebellum gives origin to none. This circumstance, which,
we ought not to lose sight of in the examination of the functions of
each part of the brain, and which will perhaps hereafter elucidate
these functions, is undoubtedly sufficient to make us appreciate
the opinion of many physicians of the last age, which placed in the
cerebellum the source of involuntary motions, and attributed the
voluntary to the cerebrum.
The cerebrum furnishes but two nerves, the olfactory and optic; these
are remarkable, 1st. in this, that their adhesion is very strong at
their origin with the brain, and that by raising the pia mater, we
cannot remove them; 2d. in this, that their softness is greater than
that of most other nerves.
The tuber annulare and its elongations, as well those that go to the
cerebrum and the cerebellum, as that which begins the spinal marrow,
furnish the motores communes of the muscles of the eye, the pathetic,
the origin of which, though posterior, is evidently derived from the
tuber annulare, the trigemini, the motores externi of the eye, the
facial, the auditory, the par vagum, the glosso-pharyngeal and the
great hypo-glossal. All these nerves are distinguished by different
characteristics. 1st. As the medullary substance is every where
exterior to the eminences from which they arise, all appear manifestly
to be continuous with this substance. 2d. Almost all begin by many
filaments separated from each other; sometimes, as in the trigemini
and par vagum, these are very numerous. The others arise, some by
one filament and others by two. 3d. Except the auditory nerve, all
have a greater consistence at their origin than these last. 4th. They
adhere but little to the corresponding cerebral portion, so that they
are almost always raised in detaching the pia mater; thus it requires
great precaution, to prevent breaking the nerves from the brain when it
is taken out of the skull. The adhesion of the pathetic, the motores
communes and the facial, is particularly weak. We should almost say,
from a slight examination, that there was only contiguity.
The spinal marrow gives origin to thirty or thirty-one pair of nerves,
viz. eight cervical, twelve dorsal, five lumbar, five or six sacral,
and to a nerve that enters the cranium and goes out of it under the
name of spinal. The following are the characters of these nerves at
their origin. 1st. They are continuous, like the preceding, with the
medullary substance. 2d. They all arise by two cords, one anterior, the
other posterior. These cords derive their origin from many filaments,
placed above each other, most usually separate and always distinct.
3d. The adhesion is much stronger at the origin of these nerves than
at that of the preceding, a circumstance that depends upon a cause
that will be hereafter pointed out. 4th. The consistence of the spinal
nerves is also very evident in their canals.
From what has been said, it is clear, that the nerves do not arise deep
in the cerebral substance, at least in an apparent manner, but take
their origin from its external surface. Many physiologists however,
have admitted an origin more remote than can be proved by examination.
They have believed that the nerves of one side arise from the opposite,
and that each pair cross each other not only in the brain, but also in
the spinal marrow. This opinion is founded upon a singular phenomenon,
viz. this, that paralysis almost always takes place on that side which
is opposite to the affected side of the brain, a phenomenon that is
frequently noticed in diseases and proved also by experiments, as has
been shown by Lorry. On the other hand, it is said that convulsions
are seated in the side corresponding with the injured side of the
brain; but this fact is more uncertain than that of paralysis, which
is incontestable. I do not believe that with our present knowledge we
can explain this last, and the anatomical opinion pointed out above, is
contradicted at the first sight.
I will make but one observation upon this singular phenomenon, and that
is, that it particularly concerns the nerves of motion, and hardly ever
affects the nerves of sensation. In fact we know, that in wounds of the
head, in consequence of apoplexy, &c. one eye, one ear, one side of the
tongue, one nostril, do not become insensible, as the muscles of one
side cease to move. We do not suddenly become paralytic on one side as
it regards sensation, as we do as it respects motion in hemiplegia.
Experiments cannot elucidate this, for it is impossible to perceive
the alterations of sensibility as we do those of mobility. However, by
compressing the brain of a dog, and thus rendering him paralytic on one
side, and then shutting each eye separately and alternately, to see if
he distinguished objects, and afterwards by presenting in turn to each
nostril volatile ammonia, or other pungent substances, I have not seen,
as it regarded the sensibility, an alteration corresponding with that
which the mobility experienced. We often observe in man a discordance
in the organs of sense. One ear hears better than the other, one eye
sees further, &c.; hence false hearing, hence a species of strabismus,
&c.; but the cause of these discordances appears to reside in the organ
itself, and not to be connected with the brain.
Moreover, it does not appear that each hemisphere always corresponds
necessarily with the nerves of motion of the opposite side. In fact,
we often see on the right side effusions or injuries of the cerebral
substance, without any alterations of motion on the left, and vice
versa.
The following are the cerebral membranes that are found at the origin
of the nerves; 1st. the dura mater forms for them a kind of canal in
the fissure through which they go out, then it quits them entirely, and
is partly lost in the cellular texture, and the remainder is reflected
upon the edges of the opening and continued with the periosteum. The
optic nerve is the only exception to this; it is accompanied in its
whole course by a fibrous canal, which goes even to the sclerotic coat,
which in this way, communicates with the dura mater. 2d. The tunica
arachnoides surrounds every nerve at its origin with a fold formed
oftentimes in the shape of a tunnel, the broadest part of which is at
the origin. By carefully raising the brain, or by opening the dura
mater of the spinal canal, we very easily discover this fold, which is
continued to the osseous opening, through which the dura mater enters,
it is then reflected upon the surface of this membrane corresponding
with the brain, forming a sac between it and the nerve. Sometimes, as
in the optic nerve and the motor externus, it penetrates the fibrous
canal of the dura mater, and accompanies the nerve to the middle of the
canal, which, consequently, is lined in part by the tunica arachnoides,
and partly by the cellular texture. 3d. The pia mater is used in a
manner that is difficult to understand, and which has not as yet been
well explained. I shall speak of its continuity upon the nerves, in
treating of their peculiar membrane.
The nerves go over a more or less considerable extent before going
out of the cranium or the spinal canal. 1st. The two that arise from
the cerebrum are much longer within than without. 2d. Among those of
the tuber annulare and its dependancies, the pathetic nerves are the
only ones that remain any length of time in the cranium before they
go out of it, and that have a greater extent there than externally;
all the others go out almost immediately. 3d. The nerves of the spine
have a much greater extent when examined lower down. Above, they become
directly external; below, they are six inches long in the canal, and
consequently pass many foramina before they arrive at their own;
hence it happens, as has been observed by Jadelot, that if we avail
ourselves of the spinous processes, on account of their prominence, to
judge of the origin of the nerves in the application of the moxa, it
is necessary, in the neck, in order to act upon a point corresponding
with the origin of any nerve in particular, to take nearly the spinous
process of the vertebra that corresponds numerically with the pair that
we have in view, whilst in the loins it is much above this vertebra
that the application should be made.
The direction of nerves at their origin is also very variable. At the
cerebrum and the tuber annulare, there is no general arrangement. But
in the spinal nerves, this direction, almost perpendicular to the
marrow above the cervical region, always becomes more and more oblique
down to the end of the lumbar region. These three things, viz. the
length in the canal, the size and oblique direction of the spinal
nerves, successively increase from above downwards in a gradual manner,
with some exceptions as to size.
Each pair of nerves, in going from the cerebrum, the tuber annulare or
its dependancies, and the spinal marrow, diverges in the two trunks
which form the pair. The olfactories alone converge, and the spinal run
nearly parallel.
II. _Course of the cerebral nerves._
The nerves exhibit different arrangements at their exit from the
osseous cavities that contain their origin.
_Communication of the cerebral nerves at their exit from their osseous
cavities._
1st. The two nerves of the cerebrum, go without communicating with
any other, to their respective destination. 2d. Those of the tuber
annulare and its dependancies begin to have communications, which are
much more evident when examined inferiorly. Thus the par vagum and
the great hypo-glossal nerves, send in going from their respective
foramina, numerous filaments to the neighbouring organs, whilst above,
the motores communes, the pathetici and even the trigemini shew this
arrangement less evidently; the auditory nerve does not communicate
with any other. 3d. The communications of the nerves of the spine are
more evident at their exit, especially in their anterior portion. The
deep cervical plexus, the brachial, lumbar, and sciatic, arise from
these communications, which are not so visible in the intercostal
nerves.
These kinds of plexuses have a particular arrangement. They are formed
in the following manner; each nerve, at its exit from the foramen,
sends a branch above and below, and also receives one; so that the
cords that succeed those that go from the foramina, arise from two or
three of these. These second cords, in dividing, send branches above
and below, receive them and form third cords; so that in the brachial
plexus, for example, when the nerves cease to communicate thus, and
are divided into separate trunks, that each may go to its destination,
it would be impossible to say correctly from which pairs they arise.
It would require a very tedious dissection to ascertain precisely from
what pairs come the median, the cubital, &c.
It is this consideration that has induced me not to describe the nerves
of the spine as it is usually done, that is, as going from such or
such pairs. I describe at first in each region the plexus that the
nerves form there in going out of the spine; thus, I expose before the
cervical nerves, the deep cervical plexus, before the brachial the
brachial plexus, and before the lumbar and sacral the plexuses of the
same name. The general arrangement, the form, the relations of these
plexuses being known, I pass to the description of the nerves that
go from them before, behind, without, within, &c. without regard to
the pairs of nerves that come through the foramina. This method has
appeared to me, moreover, to be extremely convenient for students.
Nothing, for example, is more complicated than the description of
the cervical nerves, by referring them to the pairs that first
furnished them. But understand well at first the deep plexus, arising
from the anastomoses of these pairs at their exit; afterwards class
the nerves, 1st. into internal, which go to the great sympathetic;
2d. into external, which are distributed upon the acromion and the
triangular space, bounded in front by the sterno-mastoideus and
behind by the trapezius; 3d. into anterior, which, winding upon the
sterno-mastoideus, form there with the branches of the facial a kind
of superficial plexus; 4th. into posterior, which go either to the
occiput, or to the posterior muscles of the neck; 5th. into those that
go inferiorly, as the diaphragmatic, as those that communicate with the
nervous branches of the hypo-glossal, &c. &c. In this way, you will
easily retain all the nervous distributions, because you will have one
point to which your memory will refer them all, and not to as many
centres as there are pairs.
_Internal communications of the nervous cords._
It is not only at their exit that the spinal nerves thus communicate.
The different cords of which each nerve is formed have precisely the
same arrangement, as may be easily seen in the great trunks, as in
the median, the cubital, the radial and especially the sciatic. By
separating the different cords of these nerves, we see that they are
not only in apposition longitudinally, but that they send numerous
filaments to each other. These communications do not resemble those
of the arteries, in which there is always continuity between the
communicating branches. Here there is only contiguity, and each of
the cords forming the nervous trunk is, as we shall see, composed
of filaments; now it is these filaments that frequently go from the
cord to which they belong to a neighbouring one; so that after a
short distance, the cords that began the nerve are not composed of
the same filaments as those that finish it; the whole becomes mingled
together in the course of the nerve. Thus the cords of the branches
of the brachial plexus, at its origin, are not arranged like those of
the branches that terminate it. For there is this difference between
the very evident plexuses formed by the nerves themselves and those
that are less evident formed during their course in their interior
even, viz. that in the first, it is the cords that go off and form
the interlacing, and in the second it is the filaments. I once amused
myself in tracing the filaments of the sciatic for a short distance;
now those which composed above the external cords, were found for the
most part below in the cords of the centre.
This remark proves that there are not nervous cords destined to
sensation and others to motion, and that if the same nerves do not
serve the double use, the difference is in the filaments, and not in
the cords.
In the interior of the vertebral canal, in which the nervous cords are
much insulated, for the want of cellular texture, the filaments that
compose them do not thus communicate with each other; there is not,
as without, a plexus in the interior of the nerve. This is remarked
particularly at the extremity of the canal, where the nerves run a long
course, as I have before said.
The communication of the nerves at their exit from their osseous
cavities is so general, that under this point of view it may be said
that they form on every side a kind of organ every where continuous,
an organ to which the optic, the olfactory, and the auditory nerves
only are strangers.
Besides, these kinds of communications, which are all made by
juxta-position, do not appear to have much influence upon the functions
of the nerves. Each of their cords, though belonging in its course
to many different trunks, can perform its functions in an insulated
manner; so can each filament, though concurring in its course to form
many cords of the same nerve.
I would observe with regard to this, that it is necessary to
distinguish accurately these communications from anastomoses, in which
two nervous filaments coming in an opposite direction, are confounded
and identified with each other, which is seen between those of the
facial, the sub-orbitary, the mental, &c.
_Nervous trunks._
After having thus communicated at their exit, the nerves separate from
each other and go towards the different organs. They form at first
considerable trunks, which pass through the great cellular interstices
and go over a greater or less extent. The form of these trunks is
sometimes flattened as in the sciatic; but it is most commonly rounded;
but the form does not affect nervous action, for the nerves that are
naturally round, when flattened by a tumour, perform their functions
as usual. In general, whenever it does not interfere with her design,
nature chooses the round form for the organs of animals. I would
observe also, that this form requires a system generally diffused,
and destined to fill up the spaces that necessarily exist between
round organs; this system is the cellular. It would be infinitely less
necessary, if the form of our organs was square, because there would be
less space between them.
The nervous trunks are of different length. Those of the extremities
hold the first rank in this respect, because the extremities being very
distant from the origin of the nerves, these trunks must of course
go over a certain extent before distributing their filaments. In the
trunk and the head, on the other hand, as the organs are presented
immediately to the nerves that enter them, the division into branches
is immediate, and the trunks are very short.
The nervous trunks are sometimes accompanied by a corresponding
arterial and venous trunk, as the brachial, crural trunks, &c.; at
other times, as the sciatics, and those of the par vagum, they go
separate.
_Of the nervous branches, &c._
As the trunks advance, they furnish here and there different branches;
these give out smaller ones, which send off those that are still
smaller, from which arise the last divisions. All these different
divisions take place at very different angles. The acute angle is the
most common. It is not a real origin, but merely a separation of many
cords united, that forms the branches, of one or two of these for the
smaller ones, of one cord only for the still smaller, and of separate
filaments for the last divisions. Thus this separation is made more or
less high, in different subjects. The place where it happens is never
exactly determined.
According to these divisions, the filaments which compose the cords
of each nerve and these cords themselves, are of different lengths;
the shortest separate first, then the middling; in fine, the longest
filaments of all go the whole extent of the nerve, and only terminate
where it ends. The brachial and crural nerves exhibit this arrangement
in a remarkable manner.
The nervous branches are almost all accompanied by an artery and a
vein, especially in the extremities; for in the trunk, there are
exceptions to this rule; in the neck, for example, the arteries often
cross the nerves at an angle, instead of accompanying them in their
course. In the head, many arterial branches are found thus separated
from the nervous. This circumstance is sufficient to make us attach
less importance than some authors have done, to this juxta-position of
the nervous and sanguineous systems. Moreover, if this juxta-position
was so essential, it would be seen with regard to the smaller branches;
but this never happens.
III. _Termination of the nerves._
I call that the termination, where each filament ends and not that only
where the whole trunk of the nerves terminates; so that the sciatic
terminates at the thigh, at the leg and at the foot, and not merely at
the extremity of this last. In fine, after what has been said already
and from what will be said further, the union of filaments into cords
and that of cords into trunks, is an arrangement disconnected with
their functions, and each filament should be examined separately.
The filaments of nerves have three different terminations. They are
continued, 1st. with other filaments of the same system; 2d. with the
filaments of the system of the ganglions; hence arise anastomoses. 3d.
They are lost in the organs.
_Anastomoses with the same system._
I have already observed, that true anastomoses should be distinguished,
from the junction of a cord that passes to a nerve more or less remote
from that to which it belongs, and which simply places itself by the
side of its filaments, so that it contributes with them to the nervous
cords. Thus there is no anastomosis in a plexus, in the union of the
chord of the tympanum with the lingual nerve, &c. So that though the
filaments of the different cords of a nerve pass frequently from one
to the other, so as to give to the nerve a net-work-like texture, and
not as anatomists say, a simple thread-like texture, still it cannot be
said that the cords of the same nerve anastomose with each other; there
is only juxta-position. On the other hand, the communication of the
great hypo-glossal with the cervical pairs, forms a true anastomosis,
because there is a continuity, and not merely contiguity of nervous
filaments.
If those physicians, who have considered the anastomosis as the
exclusive causes of all sympathy, had reflected how few they are in
comparison with what they appear at first view, they would have been,
by this simple reflection, led to a different opinion. In fact, it is
very evident, that though a filament is joined to a trunk, it has no
more relation to the filaments of that trunk, than these have among
themselves; that is to say, that there is nothing in common but the
cellular covering. The arterial and venous anastomoses are infinitely
more numerous than the nervous. I believe that they can perform a part
in neuralgia, in some sympathies even, a part foreign to the simple
communications of the filaments.
We can generally refer anastomoses to three classes. 1st. Two branches
belonging to different nerves, go on together, as in the example cited
above of the great hypo-glossal, and as also the branches of the facial
with those of the sub-orbitary, the occipital with the frontal, &c.
2d. The branches of the same nerve can unite together, as those of the
three portions of the trigemini. 3d. Sometimes the two nerves of the
same pair, or those of two different pairs, but coming from the two
halves of the nervous system, unite at the median line; some examples
of this may be seen in the superficial nerves of the neck, in those
of the chin, &c. This union does not take place upon the abdomen,
where the median line, entirely aponeurotic, has no nervous branch in
its texture. It is perhaps by these anastomoses that take place at
the median line, that we may explain, how certain motions can still
continue in a part affected with paralysis. This sort of anastomosis
is in general very rare. In the extremities it is evident, that they
cannot exist; in the trunk, they are hardly ever seen behind, and not
frequently before. If every pair of nerves gave examples of them, it is
clear that hemiplegia would rarely take place, because the sound side
of the brain or spinal marrow would through them have an influence upon
the nerves of the affected side.
_Anastomoses with the system of organic life._
This termination has a great analogy with the preceding, since there
are two nerves, which meeting at their extremity, are blended in such
a manner, that we cannot tell where one begins, or the other ends. I
shall treat of this in the following system.
_Termination in the organs._
The exposition of the following systems will show us the varieties
that exist as it respects the nerves. 1st. In some there are many of
them, as in the mucous, dermoid and muscular systems of animal and
organic life. 2d. In others we find fewer of them, as in the cellular,
glandular systems, &c. 3d. Some require a more attentive examination
than has heretofore been made of their nerves, which are little known,
as the serous, the medullary, a portion of the fibrous, &c. 4th. In
fine, many, as the cartilaginous, the fibro-cartilaginous, the pilous,
the epidermoid, the tendons of the fibrous, &c. are evidently destitute
of nerves.
We are ignorant of the situation of each nervous filament at its
termination; is it deprived of its covering, and does the pulp only
penetrate the interior of the fibres? In the optic nerve this last
arrangement is evident. The covering of the nerve is continued only to
the entrance of the eye, and the pulp is expanded to form the retina.
A similar expansion seems to take place in the olfactory and the
auditory. But nothing is known concerning any of the others.
ARTICLE SECOND.
ORGANIZATION OF THE NERVOUS SYSTEM OF ANIMAL LIFE.
I. _Texture peculiar to this organization._
Every nerve is formed, as I have said, of a greater or less number
of cords lying in apposition to each other. These cords arise from
filaments likewise in apposition and united together, like the cords
by cellular texture. I have already mentioned how both are interlaced
in the interior of the nerve, so as to form a kind of plexus, which
differs from the true plexus only in this, that the branches applied to
each other, do not allow us at first view to see their intermixing.
The general character of the nervous cords varies considerably. 1st.
Their size is not always the same. Those of the sciatic and the crural
are smaller than those of the brachial nerves, except those of the
median. 2d. Some nerves, as the par vagum, are formed of one cord only,
divided by many furrows. Sometimes the filaments form around it a
net-work, a very delicate kind of plexus. 3d. In the same nerve, there
is sometimes united large and small cords; in many they are all equal,
as in the sciatic. 4th. The optic nerve, though furrowed in its whole
extent, from the commissure to the eye, does not appear to have in its
interior that interlacing, that the others evidently exhibit. 5th. In
the posterior part of this nerve, and in the trunk of the olfactory,
the cords are not distinct. 5th. Most of their nerves at their origin
are separate in their filaments; the trigemini on the contrary,
exhibit a common pulpous portion, in which all their's seem to be
implanted, &c.
It follows from all these considerations and many others for which
we are indebted especially to Reil, that the internal arrangement of
the nerves varies singularly, that each presents almost a different
texture, that under this point of view they do not resemble the
arteries and veins, which are every where the same, whatever be their
size, their course, &c. These varieties however, do not affect the
intimate structure, and our business is to describe this intimate
structure even to the last fibres that we can separate. Reil appears
to me to have thrown great light upon this subject. I have repeated
exactly his experiments; they have given results very analogous to
his. Some only have appeared to me so difficult, that I have not even
undertaken them. I have added to his researches many new facts as will
be easily seen by comparing his work with this article, in which will
only be found that which rests on accurate observation; I have omitted
all the theoretical ideas that Reil has added to the facts which he
offers.
We distinguish two things in every nervous filament, 1st. an external
membrane in form of a canal, in which is contained the medulla; 2d. the
nervous medulla itself; I shall now treat of each separately.
_Of the nervous coat and its origin._
This membrane forms for each nervous filament a true canal which
contains in its interior the medulla; as the veins and arteries contain
the blood, with this difference, that this medulla is stagnant, while
the blood circulates.
The origin of the nervous coat is very evident at the spinal marrow.
It is continued with the dense and compact membrane which covers its
white substance, and which is called the pia mater, though it does
not resemble the membrane of that name which surrounds the cerebral
circumvolutions. To see this origin well, this spinal membrane should
be cut longitudinally before or behind. The medulla then appears
whitish, soft and easily raised up. If it is raised and scraped with a
scalpel or any other instrument, the immediate covering of the spinal
marrow is thus separated from either side, especially if precaution be
taken to wash it. It might be had in the form of a sac, by cutting out
a piece of the medulla of a certain extent and then pressing out the
medullary substance at the two ends. In this double experiment, the
nerves remain attached to the membrane separated from its medullary
substance, because their nervous coat is continued with it. It is
exactly as if a number of small arterial filaments went from the aorta;
the parietes of this artery would be to those of these filaments, what
the pia mater of the spinal marrow is to the coat of the nerves which
go from it. Only the nerves are white, because their medulla fills
them; whereas the canal to which they belong is transparent, because it
is deprived of its own medulla. I do not pretend however, that there is
a perfect identity between these two membranes, since we do not exactly
know the nature of either; I refer only to their anatomical arrangement.
As to the origin of the nerves contained in the cranium, those coming
from the tuber-annulare and its dependancies, that is to say, the
elongations that it receives from the cerebrum and cerebellum, have
an arrangement analogous to that of the nerves of the spine. However,
the difference of thickness and density of the pia mater establishes
differences. In fact the pia mater which covers these parts is
different from that which serves as a canal to the spinal marrow; it
is much softer, less adherent, is torn with more ease, and appears to
be analogous to that which covers the cortical substance of the brain.
The coat of the nerves of the tuber annulare, which is manifestly
continued from this portion of the pia mater, exhibits partly this
character. At the place of their union, it is more soft than in the
canal, hence the extreme facility with which, as I have observed, the
origin of these nerves is broken. Moreover, the continuity with the pia
mater is proved by the facility of raising the nerves by raising this
membrane; almost always both are attached together.
As to the nerves of the cerebrum, the olfactory, loosely covered by
the pia mater, does not appear to have a coat of its own. The optic is
evidently destitute of it from its origin to its junction with that of
the opposite side. Then it begins to be covered with it; and canals
are formed by it, filled with medullary substance, and which continue
even to the retina. Besides, this nerve differs singularly from the
others, 1st. because it has a kind of general nervous coat; 2d. because
its medullary substance is more abundant and more easily obtained, its
canals being larger; 3d. because these canals, pressed against each
other, give it the appearance in the interior of a continued body; but
by cutting it longitudinally, it is easy to see that the medullary
substance is separated there by partitions. The auditory nerve has also
a very peculiar texture.
From what has been said, it is evident that the pia mater has greater
analogy with the coat of the nerves, than any of the other membranes;
it may be said to be almost the same in the spinal canal. Observe, in
fine, that this membrane, which has never yet been well described,
evidently presents three great modifications, according as it is
examined; 1st. upon the grey substance that surrounds the whole of
the cerebrum and cerebellum, where it ¡s reddish, extremely vascular,
loose, slightly resisting, and very easily raised; 2d. upon the white
substance that covers anteriorly and posteriorly the tuber annulare and
the four great elongations that it receives from the cerebrum and the
cerebellum, where it is less red and where it begins to become more
firm, more adherent, and less easily torn; 3d. upon the whole spinal
marrow and upon the corpora pyramidalia and olivaria. It is thickened
and condensed at the furrow that separates these eminences from the
tuber annulare, then, increasing in thickness below, becoming whitish,
resisting, &c. it has an appearance entirely different from what it had
in the cranium. It might be said to be a membrane wholly different. It
has four times the thickness of the tunica arachnoides.
In most of the subjects that I have examined it is much stretched,
and compresses, if it may be so said, the medullary substance for
which it serves as a canal; so that when a small opening is made in
it the medullary substance immediately comes out. But I presume that
it is looser during life. Besides, this state of compression is much
less sensible towards the superior part than towards the middle and
inferior, on account of the difference of thickness. I would remark,
that the density of the pia mater of the spine is necessary to prevent
injuries of the medullary substance, which is very soft at one part,
and which at another is smaller than the diameter of the canal; so that
it can be shaken there; an arrangement wholly different from that of
the brain, which completely fills the cranium.
Arising in the manner we have pointed out, the coat of the nerves
passes with them through the cavity of the cranium and that of the
spine. It is very distinct in these cavities, because it is not
surrounded there with cellular texture, but only with the arachnoides,
which may be raised with great ease; instead of using the different
preparations that Reil mentions for the purpose of separating the
coat of the nerves from the cellular texture, it is infinitely more
convenient to examine this membrane upon the last nerves of the spine,
which are, as we have seen, remarkably long.
_Action of certain substances upon the nervous coat; its resistance,
&c._
Without the osseous cavities, the nervous coat embedded in the cellular
substance, adheres to it strongly, but appears evidently to be of the
same nature as in the interior. We are ignorant what its nature is,
whether it is the same as that of the pia mater, of the medulla, of the
tuber annulare and its dependancies. It appears to have great affinity
with the cellular texture. It is transparent and consequently free from
the colour of the nerves; hence why, when they have been deprived, by
alkalies, of their pulp, they lose a great part of their whiteness.
The coat of the nerves is one of the parts of the animal economy which
are hardened with the greatest ease, especially at the instant the
nerves are immersed in an acid slightly concentrated, particularly
the nitric and sulphuric. I have not observed in any other texture
this phenomenon in so remarkable a manner; the nerve is suddenly
diminished in size and twisted in different directions; now we shall
see that the medullary substance is in no way concerned in this
phenomenon. The action of boiling water produces an analogous effect;
by it the nerve is wrinkled, contracted and hardened; then, after the
ebullition has continued for a certain time, it gradually becomes
soft, and its whitish colour is changed to a sort of yellowish tint,
very different from that of boiled tendon or aponeurosis. The action
of the acids continued for some time, produces an effect analogous to
that of ebullition. To the sudden hardening like horn which the nerve
undergoes, soon succeeds a softness so great that at the end of a short
time it is easily moved under the finger, and afterwards becomes partly
dissolved.
The alkalies do not produce the horny hardening in the nervous coat
any more than in any other texture of the living economy; neither do
they dissolve it. Hence, undoubtedly, why Reil, having macerated for
some time a portion of nerve in soap-boilers lie, was able to separate
accurately the nervous coat from its medullary substance.
The action of water upon the nervous coat produces a phenomenon that is
exhibited by few others of the animal textures. Far from softening it
immediately and then reducing it to pulp, it seems in the beginning to
increase its consistence. A nerve soaked in water becomes there harder
and more resisting, and this state, at the ordinary temperature of
cellars, continues for a month and a half, and even two months. It is
only at the end of this time and frequently longer, that the texture of
the nervous coat is gradually softened, and broken, and finally ends by
being diffused like other macerated textures. I have not repeated this
experiment in a very warm temperature, which has always succeeded in
that of winter and spring.
The coat of the nervous filaments has a very great resistance, because
it is, in proportion to the medullary substance that it contains,
infinitely thicker than the membranous canal of the spinal marrow.
It is thus that the proportion between the thickness of the vascular
parietes and the fluids they contain, is much less in the great trunks
than in the small branches; the fluid considerably exceeds the solid
in the first, there is at least an equality in the second. Thus a very
small nerve would support a much greater weight than the spinal marrow.
I believe that among the textures which are arranged in filaments or in
elongated tubes, this and the arterial, next to the fibrous, afford the
greatest resistance; they surpass the venous, the muscular, the serous,
&c.
_Medullary substance; its origin._
This substance occupies the interior of the nervous canal, in the same
way as the substance of the spinal marrow fills the canal formed by
the pia mater. This medullary substance is whitish, as that of the
brain and spinal marrow; it gives the nerve its colour. It is in much
greater proportion in the optic nerve than in any other; it is found
exclusively in that part of it posterior to the junction of the two,
as well as in the olfactory. It is so abundant in the auditory that it
seems to form a great part of it. In general, I think at the origin in
the osseous cavities, it predominates over the nervous coat, but in
the course of the nerve, the nervous coat is the greatest. Hence the
greater degree of resistance of the nerves in the second, compared to
what they have in the first.
This substance appears to be continuous with the medulla of the brain,
the tuber annulare and its dependancies, and the spinal marrow. I
think, no one can deny this continuity with the origin of the optic and
olfactory nerves, in which more of this medullary substance is found
than in the other nerves. In the auditory, also, it is very apparent;
in the spinal marrow, by scraping this white substance from the
internal surface of the pia mater, so as to leave the nerves adhering
to this membrane, we see evidently at the place where these nerves go
off, that there is an elongation penetrating their nervous coat.
_Comparison between the medullary substance of the brain and the
nerves._
What is the nature of the medullary substance of the nerves? I have
endeavoured to institute a comparison between it and the cerebral
substance; there is considerable analogy under some points of view and
some difference under others.
1st. Submitted to drying in the open air, in small slices to prevent
putrefaction, the white substance of the brain becomes yellow, and
acquires considerable consistence. The nerve dried becomes yellow also,
hardens and contracts. These changes are undoubtedly owing in part to
its coat. The proof of this is that if we dry the covering that the
pia mater furnishes to the spinal marrow, a covering that has great
analogy to the nervous coat, the new qualities it acquires are very
analogous to those of the dried nerves. But this does not prevent the
medullary substance of the nerve from contributing also to the yellow
colour by the evaporation of its watery part. I will make, in regard
to this, a remark that I think interesting; it is this, that water has
an influence upon the whiteness of a number of textures which become
yellow or greyish by its subtraction, and are whitened again by its
addition. Thus we have the power of making yellow, by drying, all the
fibrous organs, the skin, &c. and of restoring them afterwards to their
primitive colour. Thus also the serous surfaces, the cellular texture,
&c. that have become greyish from drying, regain their whiteness when
immersed in water, if they have not been long dried. The epidermis of
the sole of the foot and the palm of the hand turns from grey to white,
when it has been immersed for some time in water.
2d. The cerebral substance and that of the spinal medulla easily become
putrid when submitted to the combined action of water and air; they
become of a greenish colour and have acid sufficient to redden blue
paper. Of all animal substances, I think they exhibit this phenomenon
the soonest. The nervous medullary substance, on the contrary, resists
putrefaction much longer. The nerves are among the slowest of all
the parts of the animal economy to become putrid. During life they
are often found untouched in a gangrenous limb, in the middle of an
abscess, &c. In a dead body which is putrid, they preserve their
whiteness and consistence, while the other parts are black and soft.
I have observed that the water in which the nervous system has been
macerated has but little odour, but that that in which the brain has
been macerated is fœtid. These phenomena clearly would not take place
if the medullary substance of the nerve became as easily putrid as that
of the brain. It is manifest, however, that it is especially to the
nervous coat, that the nerves owe this sort of incorruptibility; for I
have observed, that the optic nerve, in which the medullary substance
predominates, and the olfactory and auditory, which are abundantly
furnished with it, become putrid sooner than the others. I have
remarked also uniformly, that whilst the white substance of the spinal
marrow becomes putrid, its covering remains untouched.
3d. The medullary substance of the nerves, as well as that of the brain
and spinal marrow, does not seem to be susceptible of any kind of
horny hardening. This is very evident when we immerse the two last in
boiling water, in a concentrated acid, &c. We may be convinced as to
the first, by submitting to the same experiment the soft nerves that
have their nervous coat pretty distinct. To this also must be referred
the following phenomenon; when the anterior part of the optic nerve is
put into boiling water, the nervous coat becomes wrinkled, its canals
shrink, and the medullary substance not contracting in proportion, is
forced towards the extremities, which become consequently enlarged.
As this substance is in less proportion in the other nerves, this
phenomenon is less apparent in them; it takes place, however, and
this explains the small round tubercle that is seen at each end of
boiled nervous filaments; it is the medullary substance that produces
these enlargements. This phenomenon is very evident in the spinal
marrow, which, being immersed in boiling water, suffers the compressed
substance to escape, either at the extremities, or at any openings that
may be made in its covering. Thus in boiling a head, the dura mater
detached from the cranium contracts powerfully in hardening like horn,
compresses the cerebral substance which does not contract like it, and
sometimes breaks it, so that it escapes into the space that the boiling
has produced between the dura mater and the cranium.
4th. When the cerebral substance is agitated in water, it becomes
suspended in it in the form of an emulsion, as has been observed by
Fourcroy, then it is precipitated to the bottom of the vessel. A
similar emulsion is made by the olfactory nerves, the posterior part of
the optics, &c. When the anterior part of these, in which the nervous
coat is very evident, has been soaked some time in water, and commonly
even without this, a large quantity of whitish substance can be pressed
out of them, which is evidently analogous to the medulla of the brain,
and which colours the water that receives it. From the other nerves in
which the medullary substance is much less abundant, it can often be
forced out by pressure, from the cut ends of the filaments, especially
if they have been previously macerated in an alkaline solution.
5th. Boiling hardens the brain, and gives it a greyish and dingy
appearance, very similar to what is seen in ataxic fevers. The same
phenomenon takes place in the soft nerves. In the others, the nervous
coat is in too great a proportion to the medullary substance to
allow us to see what happens to this last. It is to this property of
coagulating by heat, which the brain has, that must be referred the
flaky precipitate that is obtained in a heated cerebral emulsion.
6th. All the acids that are much concentrated harden the brain very
evidently, the instant it is immersed in them. The sulphuric afterwards
softens it, and finally reduces it to pulp, if it is not diluted. The
nitric makes it yellow only, in hardening it. The muriatic has the
least action upon it. The effect of acids upon the soft nerves is
very analogous to this. In those in which the coat is very distinct,
the horny hardening of which this coat is the seat, conceals all the
sudden phenomena relative to the medullary substance. When the coat
is softened and dissolved, this substance has appeared to me to be
diminished in consistence and altered by the acids, whereas that of the
brain keeps always the same degree of hardness, if the acid be not too
much concentrated.
We all know that alkohol hardens the brain. This hardening, the
effect of acids, of boiling, and of alkohol, is a phenomenon that
the anatomist can avail himself of to give the parts he dissects a
firmness, that will enable him to examine them better. It approximates
this substance to the albuminous fluids. I say that it approximates it,
for there are still great differences between them, of which, I think,
we know but little.
7th. The alkalies have an effect upon the cerebral substance precisely
opposite to that of the acids. They make it fluid, and even dissolve
it completely after a short time. I have observed, with regard to
this, that the grey substance is much quicker altered by them than
the white, which is softened, disappears in part, but still leaves a
considerable portion that is not dissolved. From whatever part we take
these two substances to submit them to the action of the alkalies, the
result is the same. The alkalies act also evidently upon the medullary
substance of the nerves. This action, as I have said, has been of great
assistance to Reil in his experiments.
8th. Thouret and Fourcroy have discovered, that the brain, after
being buried, lessens considerably in size, and changes to a brittle
substance, capable of softening under the finger, miscible in water,
exhaling a disagreeable odour, having the properties of ammoniacal
soap, and resembling very closely spermaceti in its nature. Do the
nerves undergo a similar alteration in their medullary substance? We
know nothing at present by which we can determine this question.
9th. The muriate of soda, when sprinkled upon slices of the brain and
the pulpy nerves, increases their consistence.
10th. The digestive juices generally alter with ease the medullary
substance of the brain. I think, however, that they would have a much
more powerful action upon it in a natural than a boiled state; for
all the re-agents are in general more powerful in the first of these
states. We know that most carnivorous animals esteem the cerebral
substance delicious food. Those that feed upon birds, the parietes of
whose craniums are easily broken, almost always eat the brain first.
The weasel, the polecat, &c. furnish examples of this. Man considers
the brain as one of the most dainty parts of the animal. The nerves are
much less easily digested; but this depends wholly upon their coat,
which does not yield so readily to boiling as the other parts. For
example, the tendons, which are as hard or harder than the nerves in
a natural state, become much softer by boiling. We can distinguish in
boiled meat each of these parts. The first, in its gelatinous state, is
more pleasant and digestible.