11th. The cerebral medullary substance is very different in the brain,

the tuber annulare and its elongations, and the spinal marrow. If we

examine it attentively, in all these we must perceive the difference

in colour, consistence, hardness, humidity, and, without doubt also

in its very nature, though our knowledge is not yet sufficiently

advanced to decide with certainty upon this last point. Has the

nervous medullary substance analogous differences? I believe that it

is similar in the same nerve, but that it varies in different nerves

according to their uses. In fact, when the internal arrangement of the

cords and the filaments which constitute the nerve, differs so much,

when there are varieties in the nervous coat also, why should the

medullary substance be every where of the same nature? Certainly the

colour and consistence of that of the olfactory are different from

that which is forced out from the anterior part of the optic. That of

the auditory does not resemble that of the trigemini, &c. We have seen

that each of the organs of sense has its peculiar sensibility, which

places it exclusively in relation with particular bodies in nature,

that of the eye with light, that of the ear with sounds, &c. I think

that these differences of sensibility depend upon the difference of

organs; but I am persuaded that the organization of the nerves has much

influence, and that the optic nerve would be unfit to transmit tastes,

the auditory to propagate impressions made by light, &c. If we examine

attentively, we shall see an essential difference of structure between

the nerve of the eye, of the nostrils, the ear, and that of the taste,

which approximates, in thickness, the nerves of motion. As to the

nerves of touch, they do not require a peculiar texture; for I shall

prove hereafter that a particular kind of animal sensibility is not

necessary for this sense, but that this general property is sufficient

for it, since its accuracy depends especially upon the mechanical form

of the hand. As to the nerves that go to the voluntary muscles, as

these muscles are every where analogous and perform similar functions,

I think their medullary substance is the same. But in the par vagum,

whose destination is so different, why do not the varieties of internal

organization coincide with that of the texture which we observe in

dissecting this nerve? We may say the same of many nerves that go to

parts whose sensibility presents an entirely different modification.

This then is a comparison between the cerebral pulp and the medullary

substance of the nerves, which may throw some light upon their

difference and their analogy. I have not availed myself of all the

details of the chemical experiments that have heretofore been made upon

the brain; I have only given the principal phenomena of the action of

different re-agents, phenomena, all of which I have repeatedly proved.

The medullary substance of the nerves is not arranged in filaments.

It appears to be analogous to the white substance of the spinal

marrow which is a real jelly, stagnant in the canal of the pia mater,

which serves as a reservoir for it. Besides, examination proves this

assertion in the optic, auditory, olfactory nerves, &c. In general I

think, that this substance, as well as the cerebral, would be ranked,

if they were deprived of the vessels that run through them, rather

among the fluids than the solids, or they would form a medium of

connexion between the two.

II. _Parts common to the organization of the nervous system of animal

life._

_Cellular texture._

The nerves are entirely destitute of this texture in the interior of

the cranium, and the spine; but out of these they have a great quantity

of it. A large external layer, first covers and then connects them with

the neighbouring parts. This layer is looser than that which surrounds

the arteries. Fat often accumulates in it; sometimes, though rarely it

is the seat of dropsical effusions.

From this common layer go off different elongations which communicate

with the cellular texture of the neighbouring organs, and form a medium

of union between the nerve and these organs. Within, there are other

elongations that go between the nervous cords, and separate them from

each other, and form for them kind of canals. When a nerve has been

macerated some time in diluted nitric acid, the cords become separated

from their sheath, which is to them what the layer of which we have

spoken is to the whole nerve. These cellular canals often contain also

fat in the great nerves, in the sciatic there is always some of it.

Hence it is that when we dry these organs, there is almost always as I

have observed, a fatty exhalation upon their surface; and that, when

they are immersed in any alkaline solution, they have evidently an

unctuous and truly saponaceous deposit.

Finally new elongations going from the cellular canals that surround

the cords, cover the nervous filaments with canals still smaller.

Here, there is never any fat or serum, and the cellular texture has in

part that peculiar nature which characterizes the sub-arterial, the

sub-nervous texture, &c.; perhaps even the nervous coat is nothing but

this texture considerably condensed. Besides, the cellular texture

so connects the one to the other, the cords of the nerves, and the

filaments of these cords, that no motion can take place there.

_Blood vessels._

Each nerve receives its vessels from the surrounding trunks, which

send to it branches which penetrate from all sides to the interior.

The optic is an exception to this rule; the membrane that surrounds

it prevents the vessels from entering it laterally. An artery passes

through it in the course of its axis and sends out different branches.

In the other nerves, the arteries run first in the cellular texture

between the cords, and are of a size there more or less considerable,

according to the nervous trunks. Sometimes this size increases

considerably. For example, in popliteal aneurism, the artery of the

sciatic nerve has been seen with a caliber more than three times its

natural size.

The arteries running between the cords, send off a number of little

branches that go into all the interstices of the filaments. In fine,

from these arise the little capillary arteries which are spread upon

the coat of the nerve, cross it and are continued with the exhalants

of the medullary substance. We readily see this vascular arrangement

in the spinal marrow. Numerous ramifications are spread first upon the

dense and firm pia mater, which there takes the place of the nervous

coat; they then penetrate the medullary substance, and are lost in

continuation with the exhalants.

The veins follow in the nerves a course analogous to the arteries;

however, in carefully dissecting many great nervous trunks, I have been

convinced that their branches do not go out of the nerves at the place

where the arteries enter. This arrangement is analogous to that of the

brain, where the arteries enter below and the veins go out above.

Many authors, particularly Reil, have overrated the quantity of blood

that goes to the nerves, because, in order to ascertain it, they have

made use of fine injections which have entered the capillary system,

which does not commonly contain red blood. I am convinced by dissecting

the nerves of living animals, the only means of having an accurate idea

of what takes place in a natural state, how uncertain this method is

here as every where else.

The blood that goes to the nerves, like that which is sent to the

brain, is a stimulant that supports their action. When this stimulant

is increased the nervous excitability increases, as Reil was convinced

by rubbing the nerves of a frog, so as to redden them by the quantity

of blood that was brought there. Does this fluid, when carried in great

quantity to the nervous system, sometimes interrupt its functions,

as happens to the brain in sanguineous apoplexy? I have not had an

opportunity yet of making this observation in a very decided manner in

the great number of bodies that I have opened. Only the nerves are a

little more reddish in some cases than others. Do these cases coincide

with certain determinate diseases? I have not any knowledge upon this

point. As to the pretended compression of the origin of the nerves, by

the blood that is carried to the brain and spinal marrow, whoever has

examined the relations of the nerves with the vessels of the base of

the cranium, will see that such a compression is not probable. Besides,

most of the holes through which the little arteries penetrate into the

interior even of this viscus, have a caliber greater than that of the

arteries; so that how full soever they may be, they cannot press upon

their parietes. I can only conceive of a compression at the origin of

the nerves, from effusions at the base of the cranium.

_Exhalants and absorbents._

We cannot discover these vessels in the nerves; but nutrition supposes

their existence there. It appears that this function is performed in

the following manner; the exhalants receive from the arteries, with

which they are continuous, the medullary substance which they deposit

in the canal of the nervous coat, which is, if I may so express myself

the reservoir of this substance, that is afterwards taken up by the

absorbents.

Many think that the nervous coat is the secretory organ of this

medullary substance, which oozes out of its parietes, to lie in its

cavity. I do not believe it, 1st. because the olfactory nerve would not

then be able to support itself, any more than the posterior portion

of the optic. 2d. The cerebral membranes are not concerned with the

secretion of the pulp of the brain, they only permit the vessels to

pass, which enter this organ to deposit it there. 3d. There is the same

arrangement at the spinal marrow, the pia mater of which has so great

an analogy with the nervous coat. The vessels cross this membrane,

then losing themselves, as I have said, in the medullary substance

constantly renew it; so that if it was possible to remove this

substance without touching the vessels, these would hang loose by their

extremities in the canal of the pia mater. Thus, in some very soft

fungi, the vessels cross here and there the substance that they deposit

in their interstices, and would produce a vegetation like net-work,

if we could remove this substance and leave them untouched. 4th. In

the optic nerve the vessels evidently are not confined to the nervous

coat; they penetrate also the canals it forms, and deposit there the

medullary substance.

Every thing appears then to prove, that the nervous coat is no more

the secretory organ of the nervous substance, than the pia mater is

of the cerebral substances or that of the spinal marrow. It may have

uses of which we are ignorant; but the principal certainly is that of

a covering; it is the passive part of the nerve, the medulla being the

part essentially active.

From this way of describing the production of the nervous medullary

substance, it is evident that it does not proceed from the brain,

but that it is formed in each nerve by the means of the neighbouring

vessels. Hence why the inferior portion of a cut nerve does not decay;

why a ligature that interrupts the cerebral communications, does not

prevent the nervous nutrition; why in most paralyses in which the

nervous system ceases to correspond with this organ, it is supported as

usual.

From these and other considerations, Reil considers the nerves as

having an entirely insulated existence, as being bodies by themselves,

communicating only on one side with the brain, on the other with the

different parts. This assertion is true as it respects nutrition, but

as it regards the functions it is in part false; for the nerves are

evidently only conductors; it is from the brain that goes the impulse,

and there too is the sensation. In animals with white blood, and even

in those with red and cold blood, these functions concentrated in

the brain, in man and the neighbouring species, are, it is true more

generally spread throughout the nervous system, hence it is without

doubt, that we can remove the brain, the heart and the lungs in

reptiles without immediately destroying life; it is on this account,

that I have remarked in my Researches upon Death, that we should never

avail ourselves of experiments upon animals with red and cold blood,

to draw conclusions concerning those with red and warm blood. But in

these and in man especially, it is undeniable, 1st. that the brain is

the centre of animal life, which ceases when the action of this viscus

is destroyed, as is proved by apoplexy, asphyxia, &c.; 2d. that it has

also immediately dependant upon it organic life, though in an indirect

way, that is by presiding over the mechanical functions of respiration,

which by ceasing, stop the chemical, then the circulation, then the

secretions, &c. so that the continuance of the two lives, and a serious

injury of the brain, are two things wholly incompatible. Authors who

have written upon life, the nervous system, &c. have usually considered

them in too general a manner. The relations of the functions are

absolutely different in animals with cold blood and in those with warm;

that which is true for one, is not so for the other.

_Nerves._

Does the nervous coat receive small nervous branches? Do these small

branches penetrate the nerves, as the small arteries spread on the

coats of the large ones? Anatomical examination does not render this

probable.

ARTICLE THIRD.

PROPERTIES OF THE NERVOUS SYSTEM OF ANIMAL LIFE.

I. _Properties of texture._

Few systems exhibit these properties more obscurely than this. If we

draw a nerve, in an opposite direction, in a living animal, it is

extended with difficulty, makes great resistance, and acquires a

length but little more than what is natural to it; this appears to

depend particularly on the nervous coat. The medullary substance would

yield much more. We know how much that of the brain is stretched in the

dropsy of the ventricles. If a great trunk is distended by a subjacent

tumour, as in popliteal aneurism, by a swelling in the axilla, &c. it

is flattened down like a ribbon; its filaments are separated and lay

at the side of each other, and it is consequently much widened. Thus

distended, these filaments can yet sometimes transmit sensation and

motion, at other times these two functions are annihilated there.

In general, a sudden distension interrupts them much more certainly

than that which comes on slowly. Hence why the luxation of the head of

the humerus often occasions paralysis, whilst it rarely happens from

very large chronic tumours in the axilla. Spontaneous luxations of

the vertebræ, which always come on slowly, are rarely accompanied by

paralysis, an accident which is always the result of those that happen

from external violence. It is thus in the brain, osseous tumours,

large fungi which increase slowly, disturb its functions but little,

while the least depression of a bone of the cranium, that succeeds

a fracture, entirely deranges them. In hydrocephalus, also, a great

collection of serum has oftentimes but little effect upon sensation,

which is nearly destroyed, when a little more of this fluid than common

is exhaled in the ventricles, as happens in some kinds of apoplexy.

When a large cavity, like the abdomen, is distended, the nerves that

are there yield partly because their curves disappear, and partly

because they are really elongated; there is also a greater separation

of them.

The contractility of texture is still less evident than the

extensibility. A nerve cut transversely, does not retract at the two

ends, which remain opposite to each other, like those of a tendon.

In amputation, the end of the nerve remains longer than those of

the muscles, the skin, &c. This is sometimes the cause of a painful

pressure from some part of the dressing.

II. _Vital properties._

These are less evident in the nerves, than would be thought at first,

from the opinions of a great many physicians, who have made these

organs perform almost the whole part in diseases.

_Properties of animal life._

The nerves must be considered, in regard to sensibility, in two points

of view. 1st. We should examine that which is inherent in them. 2d. It

is necessary to consider the part which they take in that of all the

other organs.

_Animal sensibility inherent in the nerves._

This property is, of all others, the most strongly marked in the

nerves. Exposed and irritated, they cause great pain. By tying,

pricking, cauterizing, or exciting in any way a nervous filament, we

uniformly obtain that result so well known in practical surgery, and by

those who make experiments upon living animals.

This property would seem at first to establish a very great difference

between the medullary substance of the nerves and that of the brain,

especially towards the convexity of this organ; for we can almost with

impunity irritate this after having removed the cortical substance.

It is only deep in the brain that the animal sensibility becomes

strongly marked, and even there it is not so much so as in the nerves.

Observe, however, that in the experiments upon the cerebral pulp you

destroy the organ itself that perceives, that, without which it could

not have animal sensibility, and whose derangement would consequently

have an inevitable influence upon this property; whereas the seat of

perception being untouched when we irritate a nerve, the pain is more

sensibly felt. It is, in fact, principally in the medullary substance

of each nervous filament, that animal sensibility resides. The nervous

coat possesses a much less degree of it. Hence why simple contact,

without pressure, occasions but little pain; hence, also, why a nerve

can almost with impunity be immersed in a purulent, ichorous fluid,

or even in the sanies of cancer; hence why the contact of the air

occasions but little pain when the nerves are merely laid bare, as I

have had frequent occasion to see in animals; why, in a variety of

cases, different tumours, in whose atmosphere the nerves are situated,

have no influence upon them. The membrane of each filament is truly in

every case a kind of covering that protects its medullary substance, in

which the sensibility particularly resides. As to the cellular texture

which enters into the composition of nerves, it has, as elsewhere, no

connexion with this property. Hence why we can, as I have often done

upon a living animal, separate from each other, with the point of a

very delicate scalpel, the different filaments of a nerve of some

size, of the sciatic, for example, when they have first been laid

bare, without giving the animal much pain. In these experiments, it is

easy to be convinced of the kind of insensibility of the covering of

each nervous filament. It is necessary to pierce it and arrive at the

medullary substance in order to produce pain.

In experiments, the animal sensibility of the nerve seems to be

gradually exhausted, and finally ceases. I convinced myself of this

upon the eighth pair of nerves, in making my experiments upon the

injection of black blood into the brain. At the moment the nerve

is raised and drawn to detach it from the carotid with which it is

connected, the animal cries out and is much agitated; but after the

same thing is repeated two or three times, he no longer gives any

signs of pain. If we cease to excite the nerve for an hour or two, the

sensibility returns with great energy, when it is drawn again. These

experiments furnish a result very analogous to that of experiments

relative to the animal contractility of muscles, experiments that are

known to all physiologists.

The animal sensibility of the nerves has a peculiar character which

distinguishes it from that of all the other systems. It is this

character which gives a peculiarity to the pain in these organs, which

does not resemble that which has its seat in the skin, in the mucous

surfaces, &c. What particularly fixed my attention upon the difference

of pain of which each system is the seat, was the question of a man of

great mind and coolness, whose thigh was amputated by Desault; he asked

me, why the pain he felt when the skin was cut, was wholly different

from that which he experienced when the flesh was cut through in which

the nerves, scattered here and there, were divided by the knife, and

why this last sensation differed entirely from that which was felt

when the marrow was divided. This embarrassed me then, when I was

wholly engrossed in surgery, and had studied physiology but little; I

have seen since, however, that it is to be referred to that general

principle of which I have already spoken, and which determines, that as

each system has its peculiar kind of animal sensibility in a natural

state, it has it also in a morbid state, that is to say, in pain.

A very clear proof of this assertion, as it regards the nerves of

animal life, is the peculiar kind of pain that is experienced in the

tic douloureux, a kind that is unlike that of any other system. The

sciatic disease, which has its seat in the nerve of the same name,

has often been confounded with rheumatism, which affects the muscles

or tendinous parts; but the difference of pain alone is sufficient to

distinguish them. Mr. Chaussier has very judiciously taken for the

first character of neuralgia, the nature of the pain. Every one knows

the peculiar sensation of numbness and afterwards of pricking, that is

felt when a superficial nerve, as the cubital, &c. is compressed. No

other organ in the economy gives the same sensation from the same cause.

The animal sensibility of the nerves has another peculiar character,

which consists in this, that the local irritation of a trunk often

produces suffering in the whole branches. 1st. We know that when the

cubital is compressed at the elbow, the pain extends along its whole

course, and that it spreads over the whole external part of the leg,

when the peroneal suffers. 2d. In the tic douloureux of the face, in

the sciatic disease, and generally in all that class of diseases of

which Mr. Chaussier has given a sketch under the name of neuralgia, an

analogous observation may be made. 3d. When we wound, without dividing,

one of the branches of the saphena, the internal cutaneous or muscular

cutaneous, in the operation of blood-letting, the subjacent part

frequently becomes numb, then painful and swelled; the irritated point

is a centre, whence go forth, along the whole course of the nerves,

painful irradiations, the consequences of which oftentimes cannot

wholly be stopped, except by dividing the irritated trunk. Thus, in

tic douloureux, the division of the nerves has sometimes overcome the

disease, though we shall succeed less frequently here by these means

than in the preceding case, where the affection is local, while here it

is usually extended along the whole course of the nerve. 4th. I have

irritated, in a dog, the sciatic nerve with nitric acid; the whole limb

was swelled and painful the next day. I have at this time another, the

whole of whose fore limb is swelled, because I passed a pin, two days

before, through one of the anterior nerves, taking care to entangle

some of the nervous filaments. This precaution is essential, for I

passed a pin through the cellular texture that separates the filaments

of the sciatic, without producing any effect. I should observe,

however, that these different experiments do not always succeed, and

that I have irritated a nerve at one point sometimes without producing

any effect. 5th. The ligature of nerves is rarely followed by these

accidents, because the communication with the brain is interrupted, by

the very means that irritate, and because the medullary substance is

flattened and its sensibility destroyed. However accidents have often

happened from tying a nerve in the operation for aneurism, and though

there is no real danger in making the ligature, all good practitioners

advise that it should be avoided.

These different considerations prove in a positive manner, the

influence that a portion of an irritated nerve has upon the animal

sensibility of all the subjacent ramifications. Physicians do not

give sufficient attention to this cause of pain, which is often very

extensive without any apparent wound. An irritated nerve in a fracture

of the ribs, in that of a limb, in a wound, in a tumour, &c. can

produce at a distance a number of phenomena, the cause of which often

escapes us, and which we should soon discover if we reflected upon the

distribution of the branches going from the trunk of the nerve that is

near the affected part.

Why in these phenomena, is the animal sensibility of the nerve below

the affected part always raised? Why does this phenomenon never take

place on the side of the brain, though it is in this direction that

sensation is conveyed in a natural state? I know not.

No other system, among those all of whose parts are united like the

nervous system, presents the same phenomenon. The arterial, the venous,

the absorbent, never feel thus in their different ramifications, the

affections of any one part of their trunk. The cellular is not affected

at a distance by the diseases of one of its parts. In the mucous

which is continuous, a part being irritated, oftentimes others also

are affected, as when the stone in the bladder produces suffering in

the glans penis; but there is always an intermediate portion more or

less considerable, which remains without being painful; this is a real

sympathy; whereas in the other, the whole nervous trunk suffers, from

the affected part to the nervous extremities.

_Influence of the nerves upon the animal sensibility of all the organs._

After having considered the animal sensibility in the nervous system

itself, we must examine the part this system performs in this property

described in relation to all the other organs, in which it is often the

means of transmission between the organ that receives the sensation and

the brain which perceives it. So that when any point of the nervous

system suffers, as in the preceding cases, the portion of nerve that

is between this point and the brain, serves to conduct the impression.

Thus in animal contractility, the nerves are always intermediate to the

brain, which is the principle of the motion, and to the muscle that

executes the motion. There is, however, more difficulty in the first

kind of transmission than in this, which, to be explained accurately,

requires that we should distinguish two kinds of sensations perceived

by the internal sensitive principle, 1st. the external; 2d. the

internal.

The external sensations are of two orders, 1st. the general; 2d. the

particular. The general sensations are derived from the sense of

feeling, as we shall see; they indicate the presence of the bodies

that are in contact with the external organs; they give the general

impressions of heat and cold, moisture and dryness, hardness and

softness, &c.; they produce a painful sensation when the external

organs are torn, pricked, or acted upon by chemical agents, &c. These

sensations may originate upon the skin, the eye, the ear, the mouth,

the nostrils, upon the beginning of all the mucous surfaces, &c.; all

the bodies in nature may produce them, and all the external organs

may perceive them. 2d. The particular sensations are relative to

certain determinate external bodies, or to particular emanations from

surrounding bodies. Thus the eye exclusively perceives the light, the

nose odours, the ear sounds, the tongue tastes, &c. These particular

sensations are to a certain degree independent of the general ones;

thus the eye may cease to see, the nose to smell, the ear to hear,

the tongue to taste, and yet these different organs may preserve the

faculty of perceiving the general attributes of heat and cold, moisture

and dryness, &c. and may be the seat of real pain. Every day we see

patients affected with gutta serena suffering from the eye, those

affected with deafness having pains in the ear, &c. I have seen a

man that was deprived of the sense of smell from the use of mercury,

and who still would suffer very much if the pituitary membrane was

irritated, &c. It is necessary, then, to distinguish in the organs of

sense, that which belongs to the general sense of feeling, from that

which is dependant upon the particular kind of feeling that each has

separately.

If now we examine the part of the cerebral nerves in these two kinds

of animal sensibility, it appears that they are equally essential to

one and the other. 1st. This is without doubt as it regards the organs

of sense; the sight, the hearing, the smell, or the taste, could never

continue after a serious injury of the optic, auditory, olfactory,

gustatory nerves, &c. I do not speak of the touch, which does not

require, like the other senses, a peculiar modification of animal

sensibility, but only the general feeling, with a peculiar form in the

organs that are provided with it, so as to mould themselves to the

figure of external bodies. 2d. As to the general sensations, whenever

the cutaneous nerves cease entirely to act in any part of the skin, it

becomes absolutely insensible; it may be pinched, irritated, burnt,

&c. without feeling it. The perfect paralyses of sensation exhibit

in man this phenomenon, which can easily be produced in animals by

cutting or tying all the nerves that go to a limb. When the general

feeling is left in the pituitary membrane after the loss of smell, the

olfactory nerve is alone paralyzed; if the nerves that enter by the

spheno-palatine foramen, through the anterior and posterior openings of

the nostrils, cease also to act, then the general feeling is likewise

lost. It is the same with regard to the other organs of sense.

I believe, then, that the nerves are actually necessary to the external

sensations, whatever be their nature. Observe also, that all the organs

with which external bodies can be in contact, as the dermoid system,

all the origins of the mucous systems, and the organs of sense, are

provided more or less abundantly with cerebral nerves; none of them

receive the nerves of the ganglions. This external portion of the

nervous system of animal life is very considerable; united to the

portion that goes to the voluntary muscles, it forms almost the whole

of this system, which has but very few appendices in the organs of

internal life.

As to the internal sensations, they have phenomena much more obscure

than the preceding. The brain is undoubtedly the centre of these

sensations, as well as those which take place without it; in fact, if

the action of this organ is suspended by wine, opium, or any other

means, though acute pains may affect the internal organs, these pains

are not perceived. Thus when the brain has received a concussion,

though the impression of sounds, of light, of odours is made as usual

upon the ear, the eye and the nostrils which are uninjured, yet there

is neither hearing, seeing or smelling. But how do the impressions

made upon the internal organs get to the brain? Here are different

phenomena, that it is impossible to conceive of well, by supposing that

the nerves are charged with transmitting these impressions exactly like

those which are experienced by the external organs.

1st. There are organs that have the most acute sensibility upon the

slightest touch, and which however receive very few apparent nerves;

such is the medullary membrane of the long bones. 2d. Certain organs

in which the cerebral nerves evidently enter, as the liver, the lungs,

&c. can be irritated in animals, without seeming to give them much

pain. 3d. The muscles of animal life, in the structure of which so many

nerves enter, in which also the branches of these perform so great a

part as it relates to animal contractility, do not occasion much pain

when their texture is cut without entangling the nervous filaments that

penetrate them. 4th. The ligaments, that no nerve enters, are the seat

of acute pain when they are distended, as my experiments have proved.

It is the same as it respects the tendons, the aponeuroses, &c. 5th.

All the organs with the structure of which the nervous system has

manifestly no connexion, transmit however to the brain the most painful

impressions when they are inflamed, &c. &c.

I could bring many other facts, which the opponents of Haller have

carefully collected; but these are such, that we cannot hesitate to

admit, that the opinion of this celebrated physiologist should not be

entirely acceded to.

All that we know upon the internal sensations is, that, 1st. there is

an organ in which the cause of sensation is seated; 2d. that this organ

transmits to the brain the particular modifications that it experiences

in its vital forces. But we are wholly ignorant of the medium of

communication of one with the other. Hence, why, in my division of the

vital forces, I have avoided a systematic basis. The distinction of the

two kinds of sensibility, of the three kinds of contractility, rests

wholly upon the observation of facts. Such is the obscurity of the

phenomena of life, that I doubt if we shall ever be able to establish

divisions from a knowledge of the nature and essence of the vital

forces.

I observe that there is a great difference between animal sensibility

and contractility; that in the first, the nerves are in certain cases

the evident agents of communication between the organs that receive the

impression and the brain that perceives it, but that in other cases,

we know not the kind of relation; whilst in the second, it is always

manifestly by the nerves that the brain communicates with the muscles,

and that the organs can never execute a voluntary motion without the

influence of the cerebral nerves.

Let us confine ourselves to this general view, which is from accurate

observation; let us abandon reasoning, where experiments are not the

basis of it. Some modern authors have been less judicious; they have

admitted a nervous atmosphere extending more or less remotely, and

acting at a determinate distance; so that though an organ may not

receive a nerve, it is sufficient that it should be in the atmosphere

of a nervous cord to be the seat of sensations. This ingenious idea

of Reil, should be placed at the side of a great number of those that

Bordeu has scattered in his works, and which are rather proofs of an

ingenious author, than an accurate and judicious mind, hostile to

every opinion not founded on rigorous experiment. In fact, what is

this atmosphere? Is it an emanation that is constantly made at the

exterior of the nerves? Is it a fluid that is independent of them,

and that nature has placed around each nervous cord, as it has placed

the air around the earth? Is it a power that has been given to the

nerves to act at a distance without intermediate bodies? Some galvanic

experiments seem to prove something similar to this in the nerves;

but these experiments have no relation to the transmission of animal

sensibility. Moreover, when pain takes place in the middle of a very

thick tendon, in the centre of a large articulation, as that of the

knee for example, it would be necessary that the atmosphere of nervous

activity should extend sometimes even an inch. Why is there not

suffering produced, by the irritation of an insensible part that is

at the side of a nerve, or even connected with it, whilst the pain is

very acute in an inflamed part, though it is at a distance from every

nervous cord? Would the nerves then have also, a sphere of activity for

motion? But why should the contiguity of the nerve never be sufficient

to produce it in the muscles? Why is it not the same of sensation?

_Animal contractility. Influence of the nerves upon that of the other

parts._

The texture of the nerves is wholly destitute of this contractility.

No kind of sensible motion is ever observed in them; they perform

however an essential part in this property, considered in relation to

the muscles of animal life. We shall see that they are the essential

agents which transmit to them the principle of motion; so that animal

contractility always supposes the exercise of three successive actions,

viz. that of the brain, the nerves and the muscles.

The opinions of physiologists have been singularly divided upon the

manner in which the nervous influence is propagated. Some have admitted

a kind of vibration, others a fluid pervading the insensible canals

of these organs. This last hypothesis is still in much credit. What

has not been said upon the albuminous, electric, magnetic nature, &c.

of this fluid? The article upon the nerves, in most physiological

treatises, is almost wholly devoted to the examination of this

question, but I shall say nothing upon it, for we do not know any thing

that rests upon experiment. Moreover, are we not able without knowing

the mode of the nervous action, to study and analyze the phenomena of

the nerves? It is the common fault of all the ancient physiologists,

to have wished to begin where they should one day end. Science was in

its infancy when all the questions they discussed turned upon the first

causes of the vital phenomena. What is the result of it? An immense

deal of rubbish, and the necessity of finally coming to the accurate

study of these phenomena by abandoning that of their causes, until we

have observed enough to establish theories. Thus mankind have disputed

for ages, upon the nature of fire, of light, of heat, of cold, &c.

until philosophers finally perceived that before reasoning it was

necessary to have a foundation upon which their reasoning should rest,

they then sought for these foundations and thus created experimental

philosophy. Thus interminable disputes have existed in the schools upon

the nature of the soul, of judgment, &c. until metaphysicians have

perceived the necessity of analyzing the operations of our intellectual

faculties before they can know their essence. Each of the natural

sciences has almost had two epochs; 1st. that of the last age, in which

first causes were the only subject of discussion; an epoch useless to

the sciences; 2d. that in which they have begun to be composed of the

study of the phenomena only that experience and observation offer.

Physiology has still one foot in the first epoch, whilst it has placed

the other in the second. Physiologists of the present day should

advance it still further.

_Properties of organic life, considered in the nerves._

They are in general very indistinctly marked in these organs. They

want sensible organic contractility. The insensible and the organic

sensibility are there only to that degree that is necessary to

nutrition; for these properties have no other functions to support

there. Thus observe, that almost all the diseases of the nervous

system are affections of the animal sensibility, and that but very few

suppose a disorder in the organic. There is hardly ever an alteration

in the nervous texture; no tumours, fungi, ulcerations, &c. as in the

systems in which the organic properties are predominant. Thus morbid

anatomy finds but little to exercise itself upon in the nerves.

The continual motion of a part sometimes increases a little the organic

sensibility of the nerves that are found there, makes their nutrition

more active and their size more apparent; but generally this phenomenon

is infinitely less sensible in them than in the muscles. On the other

hand though the nerves may have lost the faculty of transmitting

sensation and motion, this last especially, they still preserve for a

long time the same degree of organic sensibility, and their nutrition

is the same as usual. I have many times examined comparatively

the nerves of the sound side and those of the side affected with

hemiplegia; I have never found in them any difference. It is only when

the limb becomes atrophous, which never happens except at the end of a

long time, that the nerve diminishes in size.

I have often searched to see, if, when a part, in which there are

nerves, has been a long time the seat of uninterrupted painful

sensations, the nutrition of these is altered, and consequently if

their organic sensibility is affected. I have dissected the stomachic

cords in cancers of the pylorus, the uterine nerves in those of the

womb; I have not found any sensible difference, except in two subjects,

in whom they were a little enlarged. Desault discovered also in a

body affected with carcinoma of the fingers, the median nerve of

uncommon size; but this phenomenon certainly is not as general, as

the dilatation of the arteries in this kind of tumours. As to acute

pains, like those of rheumatism, of different inflammations, &c.

however severe they may be, they have no effect upon the nutrition of

the nerves which transmit them. When the pain is seated even in the

nervous texture itself, as in the tic douloureux, there is oftentimes

no organic affection. At least Desault had occasion to open two

patients that had had that disease, and the nerves were the same on

each side. This, however, deserves further research, and it may be,

that in many cases, the internal substance of the nervous cords is a

little altered; for I preserved the sciatic nerve of a patient, who had

experienced very acute pain in its whole course, and this had at its

superior part, a number of little varicose dilatations of veins that

entered it.

_Influence of the cerebral nerves upon the organic properties of other

parts._

Have the cerebral nerves any influence upon the organic sensibility

of other parts? I think not, and this is the essential difference

that distinguishes it from animal sensibility, which we can with

difficulty conceive of, especially in its natural state and in the

external sensations, without the nervous influence intermediate

between the brain and the part that receives the impression. To prove

this assertion, let us examine the functions that depend upon organic

sensibility. These are, 1st, the capillary circulation, 2d, secretion,

3d, exhalation, 4th, absorption, 5th, nutrition. In all the phenomena

of these functions, the fluids make an impression on the solids of

which we have no consciousness, and in consequence of which the solids

react. It is by the organic sensibility that the solid receives the

impression, it is by the insensible contractility that it reacts; now

in none of these cases do the nerves appear to perform an essential

part.

1st. The capillary circulation exists in the cartilages, the tendons,

the ligaments, &c. in which the nerves of animal life do not enter.

Inflammation, which is only a derangement, an increase of this

capillary circulation, takes place in these organs, as well as in those

that are the most nervous; what do I say? where the nerves are the

most numerous, this affection is not the most frequent; the muscles

are an example of this. The tongue, whose surface alone has more than

four or even five times the quantity of nerves of the mucous surface,

is not so often inflamed as the rest of this system. The retina,

which is entirely nervous, is rarely inflamed. Nothing is more rare

as I have said, than the inflammation of the nerves themselves; the

internal substance of the brain is hardly ever inflamed. On the other

hand, examine the serous surfaces, the cellular texture, in which there

are infinitely less nerves; the capillary circulation is constantly

active there, and inflammation comes on. In the limbs of paralytic

patients, in animals in whom the nerves are cut in order to render a

part insensible, does not the capillary circulation continue as usual,

when the nervous action has ceased there? Have you ever accelerated

this circulation in a limb, or produced inflammation, by increasing

convulsively by irritation the action of the nerves of this limb? The

phenomena of convulsions and those of paralysis, are wholly distinct

and have no analogy with those of inflammation; this would not be so,

however, if the cerebral nerves had any influence upon them. In the

first phenomena, it is the animal sensibility that is altered; in the

second it is the organic; this is then independent of the cerebral

nerves.

2d. Exhalation is the second function over which this last property

presides. I refer to the dermoid system to prove that the sweat is

independent of the nerves. I would only observe here, that in the

synovial, in which there is an evident exhalation, there are hardly

any nerves; that the serous surfaces and the cellular texture, so

remarkable for this function, are, as I have said, almost destitute

of them; that whenever there are accidental exhalations, as in cysts,

hydatids, &c. the nerves have evidently no influence, as the tumour

is uniformly without them; that by acting in any manner upon the

nervous system, as by irritating the nerves, the brain, or the spinal

marrow, in order to excite this system, as by tying or cutting the

first, and compressing the second, to annihilate or weaken its action,

the cellular, serous, synovial, or cutaneous exhalations are never in

any way affected; and that finally the diseases of the nervous system

have no other influence upon this function, than what is derived from

general sympathy.

3d. As much may be said of absorption. It is during sleep that the

skin oftentimes absorbs most easily; now there is at that time, an

intermission in the action of the nervous system, as well as of that

of the brain. This intermission, to which it is periodically subject,

ought to produce one in the serous, synovial, medullary absorptions,

&c.; but yet they go on constantly. It is the same of all the functions

over which the organic sensibility presides; they are essentially

uninterrupted, though the nervous and cerebral actions are essentially

intermittent.

4th. The same observation may be made concerning the secretions,

notwithstanding what Bordeu may have said. For the rest, I refer upon

this point to the glandular system.

5th. Nutrition takes place in parts that evidently receive no nerves,

as in the cartilages, the tendons, &c.; in paralyzed limbs also its

alterations are always independent of those of the nervous system.

Those people in whom this system is the most elevated, who are the

most sensitive, are not those in whom nutrition is the most active.

In no experiment, I believe, has any one been able to influence

nutrition by acting upon the brain, the nerves, and the spinal marrow.

Marasmus undoubtedly succeeds all prolonged nervous diseases; but it

is a phenomenon common to many diseases. In palsy, the long rest, as

well as the deficiency in the action of the nerves, has an influence

in producing atrophy; but it is a long time before this manifests

itself. Who does not know that often at the end of two, three, or

four years even, the diseased limb is exactly of the size of the well

one? Moreover, natural nutrition obeys the same laws as accidental

nutrition, as that which takes place in the formation of fungous and

sarcomatous tumours, and fleshy granulations. Now the cerebral nerves

have evidently no connexion with all these productions; they are

never found in them; a phenomenon very different from that which is

offered by the arterial system, which is almost always developed in a

remarkable manner in these tumours. In fine, we shall see hereafter

that the nerves do not increase in proportion with the parts to which

they are distributed.

From what has been said, it is evident that all the phenomena, over

which preside what are commonly called the tonic forces, viz. organic

sensibility and insensible contractility, are completely independent of

nervous action; and consequently that these properties would not, like

those of animal life, require this action. Each kind of sensibility

has its morbid phenomena over which it presides. Inflammations,

suppurations, the formation of tumours, dropsies, sweating,

hemorrhages, disorders of secretions, &c. &c. belong to the alterations

of the organic sensibility, whilst every thing like spasm, convulsion,

paralysis, trance, torpor, injury of the intellectual functions, &c.

&c. every thing, in fact, which tends in diseases to destroy our

relations with surrounding bodies, belongs to the alterations of animal

sensibility or contractility, and implies a greater or less degree of

disorder in the nervous system.

In general, the diseases that affect the functions of animal life are

of a nature wholly different from those which destroy the harmony of

organic life. They have not the same character, the same progress,

and the same phenomena. Place on one side the injuries of the

external senses, blindness, deafness, loss of taste, &c.; those of

the internal senses, mania, epilepsy, apoplexy, catalepsy, &c.; those

of the voluntary motions, &c.; on the other, fevers, hemorrhages,

catarrhs, &c. and all the diseases that disturb digestion, circulation,

respiration, secretion, exhalation, absorption, nutrition, &c.; we

shall then see what an immense difference there is between them.

Physicians have used too vaguely the term nervous influence. If in

medicine, as in physiology, we had accustomed ourselves to use those

expressions only to which was attached a precise and definite meaning,

this would have been employed much less frequently.

It appears that the nerves have some influence still unknown, in

the production of animal heat. The following facts relate to this

influence. 1st. In aneurism, the ligature of the nerve is often

followed by a sensation of general torpor and coldness in the limb.

2d. Sometimes, in hemiplegia, the affected part is of a temperature

below what is natural, though the pulse may be as strong in this side

as the other. 3d. One of the characters of ataxic fevers, the principal

seat of which is in the brain, is the remarkable irregularity in the

temperature of the different parts of the body. 4th. Animals, with a

strongly marked nervous system, as quadrupeds and birds, are those of

all others, in whom the degree of natural heat is the highest. 5th.

I knew a person that had had the cubital nerve divided by a piece

of glass above the pisiform bone, and whose little and ring fingers

of that hand uniformly remained colder than the rest. 6th. Often in

luxations, the compression of the nerves by the heads of the bones,

produces an analogous effect, &c. &c.

However, the heat is not always increased, when the nervous action is

augmented, nor is it always lessened when this action diminishes; there

are as many cases in which the heat appears to be independent of the

nervous system, as there are where it appears to be connected with it;

so that we are still confined here to the collection of facts, without

drawing general conclusions from them.

_Sympathies._

I divide what I have to say upon the sympathies of the nerves, as I did

that which was said upon their vital forces; that is to say, I shall

examine first the relations that each nerve has with the other parts,

then I shall speak of the general influence that the nervous system

exercises upon the sympathies and of the part it takes in them.

_Sympathies peculiar to the nerves._

There is no doubt as to the relations of the nervous with the other

systems, of those which it has with the muscles and with the brain.

In fact, these relations are natural; for the one cannot be affected

without the other's feeling it. These three organs can in this respect

be considered under one point of view. Thus too, the pulsation of the

arteries is always connected with the action of the heart, &c. Every

idea of sympathy excludes that of a natural connexion of functions.

Barthez is mistaken upon this point. I speak only of the unnatural

relations of the phenomena that take place between an organ and a

portion of the nervous system which is not connected with it by the

natural order of life; now, thus considered, the nervous sympathies are

very numerous.

1st. Two nerves of the same pair often sympathize with each other. We

know in medicine the relation there is between the two optic nerves;

the one being disordered in its functions, the other frequently becomes

so. This happens more rarely with regard to the ears, the nostrils, &c.

though it sometimes takes place in them. Often in neuralgia (a word

which I adopt very willingly and which is wanted in the science to

express a class of diseases every genus of which has a distinct name)

often I say in neuralgia a nerve being painful, the corresponding

one becomes so sympathetically. I have an example of this at present;

it is a woman, who for two months has been afflicted with sciatica of

the left limb. In changes of weather, a pain precisely similar spreads

itself along the course of the nerve of the opposite side. I applied

two blisters upon the thigh first affected; the pain disappeared in

both sides at the same time at the end of twelve hours. Thus, in order

to cure pains in both eyes, it is oftentimes sufficient to act only

upon one, &c.

2d. Sometimes two nerves of the same side sympathize without belonging

to the same trunk. Thus an injury of the frontal nerve has been many

times followed by a sudden blindness in consequence of the affection of

the optic nerve, &c.

3d. In other cases it is the branches of a common trunk which influence

each other reciprocally, as when a branch of the superficial temporal

is wounded in the operation of arteriotomy, the whole face, which also

receives its nerves from the fifth pair, becomes painful, &c.

4th. At other times, it is not among themselves that the nerves

sympathize, but with other organs; and then sometimes they influence,

at others they are influenced.

I say first they influence; thus a nerve being irritated in any way,

a number of sympathetic phenomena take place in the system. Diseases

frequently show these facts. It is thus in tic douloureux and analogous

diseases, in which the nervous texture is particularly affected,

sometimes the animal sensibility is raised in various remote parts,

and hence the pains that are often experienced in the head, in the

internal viscera, pains that cease when the cause that supported them

has disappeared. Sometimes it is the animal contractility; hence the

convulsions that occasionally take place in the muscles that receive

branches from the affected nerve. In some cases it is the sensible

organic contractility which is sympathetically excited by the nervous

affections. Thus in the paroxysm of neuralgic pains there is often

spasmodic vomiting, the action of the heart is hurried, &c. We can by

experiments produce the same phenomena. Thus by acting upon the nerves

of the superior or inferior extremities, by irritating them any way

after they have been laid bare, I have frequently produced vomiting, or

convulsions in muscles that were in no way connected with the nerves I

irritated.

In the second place, the nerves can be influenced by diseased organs;

thus in many acute and chronic affections, sympathetic pains spread

along the course of different nerves, particularly in the extremities.

As the animal sensibility is the predominant property of the nerves,

it is almost always that which is brought sympathetically into action.

Physicians have not distinguished with sufficient accuracy in the pains

of the extremities, that which belongs to the nerves, from that which

has its seat in the muscles, the aponeuroses, the tendons, &c.

_Influence of the nerves upon the sympathies of the other organs._

Authors have been much divided upon the cause that supports sympathies.

How can an organ which has no relation with another that is frequently

very remote, influence it so as to produce serious diseases there,

merely because it is itself affected? This singular phenomenon is often

witnessed in a state of health; but it is so wonderfully increased in

diseases, that if we could remove from them the symptoms that are not

exclusively dependant upon the derangement of the function particularly

affected, we should find but little difficulty in their study or

treatment. The moment an organ is affected, all the rest seem to feel

simultaneously the disorder it experiences, and each seems to be

agitated in its own way in order to expel the morbific matter that has

seized upon one of them.

Most authors have believed that the nerves were the general means of

communication that connected the organs with each other, and also

their derangements. The anastomoses have appeared to them to be

destined to this use; and with this opinion, some have thought that the

brain was always mediately affected, but this others have rejected.

The communication of parts by the means of blood vessels has also

been thought to be a cause of sympathies. Others have admitted the

continuity of the cellular texture; some, that of the mucous membranes.

I shall not undertake to refute in detail these different hypotheses;

I would observe only, that as no one is applicable to all the cases of

sympathy, it is because the aberrations of the vital forces have been

described in too general a manner; it has been thought that a single

principle presided over them, and this principle has been sought for.

But in order to ascertain the cause that supports sympathies, they

must be divided, as I have divided the vital properties; for as each

of these properties supposes different phenomena, so the sympathies

that put them in action, differ also. To make this distinction of the

sympathies more evident, let us suppose a diseased organ, the stomach

for example; it becomes then a centre, whence go forth numerous

sympathetic irradiations, which bring into action in the other parts,

sometimes the animal sensibility, as when pains of the head come on;

sometimes contractility of the same species, which is the case when

worms in the stomach produce convulsions in children; sometimes,

sensible organic contractility, which, raised in the heart by certain

pains in the stomach, occasions fever; oftentimes the insensible

organic contractility and the organic sensibility, as when the gastric

affections increase sympathetically the secretions that take place upon

the tongue, and produce there a mucous coat. There are then sympathies

of animal sensibility and contractility, and of organic sensibility and

contractility. This being premised, let us examine the cause of each.

1st. When the animal sensibility is sympathetically raised in a part,

this does not always depend on nervous communications; for oftentimes

the organ in which is the material cause of pain does not receive any

nerves, as the tendons, the cartilages, &c.; then it cannot communicate

by them with that in which this pain is found. On the other hand we

have seen above that it is still very uncertain if the nerves are the

only agent that carry to the brain the internal sensations; we cannot

say then that the affected organ acts at first upon the brain by their

means, and that this reacts afterwards upon the part in which the

pain is seated, by the nerves that go to it. Can we conceive that the

cellular texture should be an agent for the communication of pain,

which is insensible to it itself? Observe also that the parts that are

the most abundantly supplied with this texture, as the scrotum, the

mediastinum, &c. are not those that sympathize the most. The same is

true of the blood vessels, which, by their nature, are not fitted to

transmit animal sensibility, and which besides do not exist in all the

organs.

It appears that all sympathetic pains are nothing but an aberration of

the internal sensitive principle, which refers to a part a sensation,

the cause of which exists in another. Thus when the extremity of the

stump gives the patient pain, who has just undergone amputation, the

sensitive principle perceives the sensation correctly, though it is

deceived as to the place whence it comes; it refers it to the foot

which no longer exists. It is the same when a stone irritating the

bladder, produces pain at the glans penis. Thus all sympathy of animal

sensibility is characterized by the integrity of the part in which we

find the pain, and by the cessation of this sympathetic pain, when the

cause that acts elsewhere has ceased. It is then probable, when a part

suffers sympathetically, that that which is the seat of the material

cause of the pain acts first upon the brain, either by the nerves, or

by some means with which we are unacquainted, and that when the brain

perceives the sensation, it is mistaken as to it, and refers it to a

part from which it does not arise; or it refers it at the same time to

the part from which it arises, and to another where it does not; this

happens frequently. The stone for example, produces suffering at the

same time in the bladder and at the end of the glans penis.

These aberrations of animal sensibility then exist entirely in the

brain; it is an irregularity, a derangement of perception; this

irregularity presents phenomena analogous to the following; we often

refer to the skin a sensation of heat, as we shall see, though caloric

is not disengaged there in a greater quantity than usual. We know that

oftentimes the sensations of hunger and that of thirst are purely

sympathetic, and that the cause which produces them in a natural state

does not then exist in the stomach or intestines. We know the illusions

of vision, of hearing, of the smell even, &c. We have not studied

sufficiently the irregularities of perception; those of the memory,

the imagination, the judgment, &c. have been analysed. These, however,

have been almost forgotten. They perform the greatest part in animal

sensibility.

2d. Animal contractility supposes constantly nervous action, when it

is put in exercise sympathetically. In fact we shall see that this

property cannot be exerted without the triple action of the brain,

of the nerves that go to the muscles that move, and of the muscles

themselves. When a muscle of animal life is brought into action by the

irritation of any distant organ, by the distension of the ligaments

of the foot for example, this organ acts at first upon the brain,

which then reacts by means of the nerves upon the voluntary muscles

that are concerned in convulsions. The following is an experiment by

which I satisfied myself of the cerebral and nervous influence in

the sympathies that occupy us. I cut all the nerves of the inferior

limb of one side, in different animals, and I afterwards irritated in

a thousand different ways, very irritable parts, as the retina, the

pituitary membrane, the marrow of the bones, &c. I produced in this way

a number of sympathetic phenomena, sometimes of organic contractility,

as vomiting, involuntary evacuations of urine, fecal matter, &c.

sometimes of animal contractility in the muscles whose nerves remained

untouched. But the muscles whose nerves were cut, were never brought

into action. I have very frequently repeated these experiments, which

would have certainly produced results, if the nervous communications

could, without the intervention of the brain, make the muscles

of animal life contract. I would observe upon this subject, that

sufficient regard has not been paid in experiments upon sensibility, to

the sympathetic phenomena. I do not know even that these phenomena have

been the object of any experiments upon animals, before those of which

I have here given the first results, and which I propose to multiply

under other points of view. There are then two things in all sympathy

of animal contractility, viz. 1st, the action upon the brain of the

organ that suffers, by means, of which as yet we know but little; 2d,

reaction of the brain upon the voluntary muscles. In this last period

of sympathy, the nerves of animal life are the agents constantly

necessary.

3d. The cerebral nerves and brain have evidently no connexion with

the sympathies that put in action sensible organic contractility

or irritability. If they had, the affected organ would first act

upon the brain, and this would react upon the involuntary muscle;

thus, when tickling produces vomiting, there would be an action of

the skin upon the brain, and of the brain upon the stomach. Now

the brain never exerts any influence upon the involuntary muscles;

whatever be the irritation that the nerves experience which go to

them, the muscles remain unaffected. Then although the brain may be

sympathetically affected, it does not react upon the involuntary

muscles; the cerebral nerves then have no connexion with the sympathies

of sensible organic contractility. The continuity of the membranes is

not a more substantial cause, and this is the proof of it. We know

that by irritating the uvula, the stomach heaves; now as the mucous

surface of the one and the other is the same, we might attribute this

sympathetic phenomenon to this circumstance. I have then made a wound

in the side of the neck of a dog; taken hold of the œsophagus and cut

it transversely; the uvula has been afterwards irritated; the dog,

notwithstanding the interruption of continuity, made efforts to vomit

as before. Let us acknowledge then that we do not know the cause of the

sympathies of sensible organic contractility.

4th. As much may be said of the sympathies of organic sensibility

and insensible contractility. We have proved that the nerves have

no influence upon these two properties; that by acting upon them

we neither increase or diminish them in any manner, and that their

diseases do not disturb the functions over which these properties

preside. Then when they are sympathetically disordered, the nerves

appear to have no connexion with these phenomena. Thus, 1st, every

sympathetic exhalation, as the sweats of phthisical patients, certain

serous infiltrations that take place almost instantaneously, &c.;

2d, all secretions of the same kind, as those which appear in a

number of diseases afford us examples of them, &c.; 3d, all analogous

absorption, the three functions over which the preceding properties

preside, are evidently unconnected with the nervous influence of animal

life. I shall say the same of the cellular, vascular influences, &c.

Certainly we have no data, by which we can explain how these means of

communication produce sweat when the lungs are affected, and saliva in

the mouth when the membrane of the palate is irritated, &c.

From all that has been said it follows, 1st. that the sympathies of

animal sensibility appear to be in the greatest number of cases an

aberration of the principle that perceives in us, and which is deceived

as to the place in which the causes of sensation act; 2d. that the

sympathies of animal contractility require inevitably the intervention

of the brain, but we know not how the part affected acts upon this

viscus, though we know very well how this viscus sympathetically

excited reacts upon the muscles to make them contract; 3d. that the

causes of the two kinds of organic sympathies are absolutely unknown

and that a thick veil hides the agents of communication which connects,

in this case, the organ from which the sympathetic influence goes to

that which receives it.

It is this obscurity of the sympathetic causes, that has made me

entirely neglect every kind of hypothetical opinion, in classing

the sympathies in this work, in which I examine them in each system

of organs. I have had regard only to a natural division, to that

indicated by the vital forces of which the sympathies are but an

irregular exercise. Now by limiting ourselves to the most rigorous

observation, it is evident that this division is the only one that is

admissible; and I believe that there is no other to be employed, until

our knowledge shall be sufficiently extended to admit of their being

classed by the causes that produce them, and not by the results they

present.

Besides I cannot recommend too strongly the necessity of distinguishing

what belongs to them from that which arises from the natural connexion

of functions. Observe what takes place in syncope, apoplexy and

asphyxia; one organ is disordered; all the others soon cease to act.

Sympathies have no part in these phenomena. Physicians have been

much embarrassed by classing these affections, sometimes as if they

belonged to the nerves, at others to the sanguineous system, &c. This

is what takes place in each.

1st. The heart first ceases to act in all syncopes, whether they arise

from passions of the mind, disagreeable odours, &c. The circulation

being stopt, the brain is no longer excited by the blood; it ceases

its action, and the whole of the animal life is interrupted. The

organic life that the blood supports, is thus suddenly annihilated. 2d.

Asphyxia commences in the lungs. Respiration is deranged; it sends to

the brain blood that cannot excite it; this ceases to correspond with

the senses, to determine involuntary motions, &c. &c. 3d. It is in the

brain that apoplexy has its first seat; thus animal life is immediately

interrupted; then, when it is very severe, the brain not being able

longer to support the motions of the intercostal muscles, these motions

are stopt; the mechanical, then the chemical action of the lungs

ceases; circulation cannot go on, and organic life is interrupted. We

see then, that in all the phenomena of these affections, the injury of

one organ, produces, by a natural consequence, the suspension of the

action of the others.

This is wholly different in the sympathies. Thus the functions of the

skin being suspended, sometimes the lungs, sometimes the stomach,

and sometimes the intestines, feel it and are affected by it; these

sympathetic phenomena may manifest themselves or may not; on the

contrary, whether it be the cerebral, pulmonary or cardiac action,

that is deranged, it is impossible but that the others should be

consequently affected.

III. _Properties of reproduction._

Are the nerves reproduced when they have been cut? The experiments of

many distinguished anatomists evidently prove that they are. What is

the manner of this reproduction? If we examine the results of these

experiments it is easy to see that there is nothing peculiar in the

nervous system, that it is a simple cicatrization analogous to the

callus of bones, to the cicatrix of the skin, &c. When a nerve has

been cut, its two ends inflame, the cellular texture that it contains

sends forth granulations by the property of reproduction that it

possesses. These granulations meeting, form adhesions that unite the

two divided ends of the nerve. As the cellular texture, the means of

union, grows from the cut extremity of the nervous coat, as well as

from that which is between the cords, it partakes of the nature of

the nervous coat, and becomes a parenchyma of nutrition, whose mode

of organic sensibility is analogous to that of the nerves, and whose

vessels deposit there medullary substance, which gives a new appearance

to the nervous cicatrix, and makes it resemble very nearly the texture

of the nerves themselves. However, as the granulations arising from

the divided ends are not made in a regular manner, there is never at

the place of union a thread-like arrangement as there is in the nerve

itself. Thus the callus of a long bone, though analogous to this bone,

is never regularly arranged like it in longitudinal fibres; thus a

cutaneous cicatrix has always an irregularity in its organization,

which arises from the irregular manner in which the parenchyma of

cicatrization has been developed.

The cicatrization of nerves is then analogous to that of bones. In

the first period there is inflammation; in the second, growth of the

cellular texture which is to serve for the nutritive parenchyma; in

the third, adhesion of those parts that have grown; in the fourth,

exhalation of the medullary substance into the parenchyma. It is

this medullary substance that makes this cicatrix differ from the

osseous, in which phosphate of lime and gelatine are deposited, from

the muscular, in which there is fibrin, &c. Sometimes there is an

enlargement in the form of a ganglion, at the place of the reunion of

the nerves; this depends upon the greater granulation of the cellular

texture. Thus sometimes the callus is enlarged; at others, if the

contact has been exact, we perceive but a slight difference; these are

varieties that do not affect the nature of cicatrization.

It follows from this, that the regeneration of the nerves, which has

lately been the object of much research, and which Cruikshank, Monro,

&c. have particularly demonstrated, has nothing peculiar in it; that

it is only a consequence of the general laws of cicatrization, and a

proof of the constant uniformity of the operations of nature, though

these operations present at first sight different results. A nerve,

that is cut out in its whole course, is never reproduced like a nail,

or the hair, which take a length, form, and appearance exactly the same

as they had before they were removed. It is under the point of view

that we have presented them, and not under this last, that the nervous

reproductions should be described.

ARTICLE FOURTH.

DEVELOPMENT OF THE NERVOUS SYSTEM OF ANIMAL LIFE.

I. _State of this system in the Fœtus._

The nervous system of animal life is one of the first that is

developed. If the heart is the first that has motion, the brain is the

first that has any considerable size. The disproportion of the head to

the other parts is remarkable in the first periods after conception;

its size is monstrous when compared with that of the subsequent ages.

Now it is evident, that it is the brain that produces this, and that

the increase of the size of the bones and the membranes that surround

it, is owing to it.

We may say that by creating first the heart and the brain, and

developing them much sooner than the other organs, nature wished first

to establish the foundations of the organization of the two lives. For

on the one hand, it is the brain which is the centre of animal life;

it is to this that all the sensations are referred; it is from it

that all the voluntary motions proceed. On the other hand, by sending

the blood towards all the organs, the heart evidently presides over

the circulation, the secretions, exhalations, nutrition, &c. which

compose by their union organic life. When these two essential bases

exist, nature begins to build, or rather develop around them the double

organized edifice, which produces on the one part a communication

between the animal and external bodies, and on the other nourishes it.

Notwithstanding these early developments, the brain is not like the

heart constantly active; its two great functions, relative to sensation

and motion, are almost nothing. The intellectual functions also have

but a very obscure action, if they have really commenced at all. The

brain is then, if we may so say, in the expectation of action; it

has not acted; it requires the excitement of external bodies. I do

not say, however, that its inactivity is necessarily entire. It can

undoubtedly perceive certain internal motions that take place in the

body, and especially the pains that arise there; for if the organic

diseases can produce the death of the fœtus, why does it not suffer

pain in these diseases? Perhaps the brain is so much the more sensible

to it, as it is not diverted by the external senses. The difference of

the external and internal sensations, is a question that deserves to

be attentively considered. We have seen that the first are uniformly

transmitted by the nerves and that the mode of transmission of the

second is uncertain. On the other hand the phenomena, the sensation,

the impression, &c. are not the same in each; so that an examination of

their relations and their differences is essential. This examination

would have much influence upon the knowledge of the kind of animal life

that the fœtus can enjoy. Whatever it may be, there can be no doubt but

that it is infinitely more contracted than after birth.

The softness of the brain is very great in the fœtus; it is truly a

kind of fluid, that the arteries, or rather the exhalants that arise

from them deposit in their interstices. These arteries are then

extremely numerous; as the brain has a very evident reddish tinge.

When it is cut in slices, numerous streaks of this colour are observed

in its substance. The two portions, the cortical and medullary, are

infinitely less distinct than afterwards, because the second is much

less white. The caustic alkali dissolves them at this period of life

with great ease. The first effect before a complete solution, is to

change the cerebral substance into a glutinous, transparent and viscous

matter, a little reddish however, and ropy, almost like the white of an

egg. I discovered nothing similar to this in my experiments with the

brain of an adult when treated with caustic alkali. The acids coagulate

the cerebral substance of the fœtus, it does not however attain by

them a degree of hardness equal to what they produce in the subsequent

periods of life.

The extreme softness of the brain renders its dissection very difficult

in the fœtus.

The nerves of animal life have a development proportional to that of

the brain. All of them are very large compared to the other parts; thus

the fœtus and the young infant are the most proper for the study of the

nervous system, as the less development of the other systems renders

this more apparent. Their medullary substance is, like the cerebral

and that of the spinal marrow, very soft and even almost liquid under

the finger; in this state we can see it in the anterior part of the

optic, in which it is very evident though contained in the canals

of the nervous coat, in the posterior part of the same nerve, and in

the olfactory where it is found by itself, in the auditory in which

it predominates, and finally at the origin of each pair, where its

proportion to the nervous coat is very evident.

In all the other nerves it is much more difficult to examine well

this medullary substance, because the nervous coat that contains it,

is as much or even more developed in proportion to what it will be

afterwards. Hence it is that the nerves are very hard and resisting

in the fœtus; and that they can support weights proportionably very

great. Maceration in water, at a moderate temperature, increases this

resistance as in the adult, and renders the nerve harder without

increasing its size. We should say that this fluid acts at first upon

the nervous coat, in an opposite manner to what it does upon the other

animal substances; finally it softens it also, and renders it almost

liquid.

The blood vessels are proportionably much larger in the nerves of the

fœtus than in those of the adult. These nerves have in their whitish

colour, a livid tinge that arises from the kind of blood that enters

them; it is the same phenomenon as that of the brain.

The development of the cerebral nerves in the first age presents a

phenomenon which essentially distinguishes it from the development of

the arteries. These last always follow the increase of the parts to

which they go. Thus, the face proportionably less developed in the

fœtus, has less large arteries. It is the same of the viscera of the

pelvis, whose very small arteries receive but little blood, which

does not penetrate and dilate them until the umbilical are closed. On

the contrary, the size of the cerebral, gastric arteries, &c. is very

considerable. The nerves are absolutely independent in their increase,

of that of the parts to which they are distributed. The olfactory,

whose organ is so contracted in the fœtus, has the same proportion as

the optic and the auditory, whose organs are already so much developed.

It is the same of all the nerves of the voluntary muscles; their

proportion of development is uniform, though the muscles vary in their

size, according to the regions. If without regard to these regions, we

examine in a general and comparative manner the nervous, cerebral and

animal muscular systems, we shall see that the first then predominates

manifestly over the second, while in the adult it is the muscles, which

proportionably to what they were in the fœtus, surpass the nerves that

are sent to them. The par vagum which is distributed to organs whose

increase is not in the same relation, presents nevertheless the same

proportion of size as afterwards, in its different branches.

This double opposite arrangement of the two systems the arterial and

nervous cerebral, proves on the one part, the immediate relation of

the first with the increase and nutrition, and on the other the small

influence that the second exercises upon them.

The nerves are, like the brain, principally inactive before birth,

though they have a great development. It is to this that must be

attributed the constant absence of their affections at this period.

The nerves are always found in the fœtus, whereas the brain, and even

the spinal marrow are sometimes wanting; this is what constitutes

acephalic subjects. I shall say elsewhere how the fœtus can thus exist.

I would only remark here that the heart, the liver and the other

principal viscera of organic life, are on the contrary rarely deficient

in the fœtus. Why? Because all the essential organs of this life are

necessary, for growth, vegetation and nourishment, phenomena that can

take place without the cerebral influence which is principally destined

to preside over animal life, which is not particularly in exercise

until birth.

II. _State of the nervous system during growth._

At birth the animal nervous system experiences a remarkable revolution,

in consequence of the red blood that penetrates it. Heretofore black

blood only circulated in its vessels. The sudden difference that the

circulation experiences, has a manifest influence upon its functions.

In fact the least foreign substance, differing from red blood, which

during life is forced towards the brain by the carotid, is sufficient

to produce there a remarkable derangement, and oftentimes even death,

as I have frequently convinced myself. Why? because it is not only as a

vehicle of nutritive matter, that the fluid sent by the arteries acts

upon the brain, but also as an excitant, a stimulant. The change of

excitement which the brain suddenly experiences at birth, inevitably

increases its vital activity, gives it that which is new and renders it

fit for the functions it has never before performed, those of receiving

sensations.

Asphyxia is real always when the lungs are not developed after birth,

when they do not receive air and consequently do not send red blood

to the brain. Some muscular motions may undoubtedly be made; but

animal life never begins in its perfection, until the organs that

execute it are influenced by red blood. This blood is a general cause

of internal excitement. This direct acts simultaneously with the

sympathetic excitement that the brain experiences from the skin and

mucous surfaces, which the external agents act upon immediately after

the exit of the fœtus from the womb. The lungs and the brain influence

each other reciprocally at this period, the first by sending red blood

to the second, and this by putting in action the diaphragm and the

intercostals, which make the air, that is necessary for the production

of this red blood penetrate the lungs; hence we see that other

excitants act before that of this blood, since before its formation,

the brain has already in it a principle of motion.

Besides, the brain and the whole nervous system are the more powerfully

excited by the new principles that the blood has derived from the air,

as, 1st. their vessels are in proportion larger and more numerous than

afterwards; and, 2d. as all the cerebral arteries enter at that part

of the base of the brain, where is found the origin of the nerves, and

which is without doubt the most sensitive part of the whole organ.

There is certainly a very great difference between asphyxia that

happens to an adult, and the state in which the fœtus is found, since,

if the first is prolonged, organic life ceases, while this life is

in full activity in the fœtus. Thus there is no resemblance in the

composition of the black blood in the arteries in asphyxia and that in

the arteries of the fœtus. These two states, however, have a sort of

analogy, especially under the relation of the remarkable diminution,

of even the absence of animal life, which characterize both. Now in

producing asphyxia in an animal at will, by fixing a stop-cock upon

the wind-pipe, I have always observed that this life is annihilated

when the black blood penetrates the brain, and that when it is in part

suspended, it suddenly revives and re-appears by opening the stop-cock,

and permitting red blood to enter the brain, nerves, and all the parts.

These experiments can, then, to a certain point, give us an idea of the

part the red blood takes at birth, in the development of animal life; I

say the part, for it is not, as we shall see, the only cause that puts

it in action.

For a long time after birth and during the whole of the growth, the

nervous system and the brain, which is the centre of it, predominate

in their development over the other systems; this predominance is not

uniform at all the periods; it diminishes at puberty, when the nervous

system is in equilibrium with the others, and the genital organs

succeed it in superiority.

This predominance of the nervous system in the infant has an influence

on the one hand on the sensations, on the other upon the voluntary

motions.

The first influence is very striking. Infancy is the age of sensations.

As every thing is new to the infant, every thing attracts its eyes,

ears, nostrils, &c. That which to us is an object of indifference, is

to it a source of pleasures. As a man receives great enjoyment from

a show he never witnessed before, which is blunted by habit if often

repeated. It was then necessary that the nervous cerebral system

should be adapted, by its early development, to the great degree of

action which it is then to have. In fact, all the organs that receive

external impressions, the nerves that transmit them, and the brain

that perceives them, are really in the infant when awake in permanent

excitement, who in the midst of the same objects as the adult, fatigues

these organs three times as much as he to whom a great part of these

external objects is indifferent, because they have heretofore excited

him. Thus observe that the periods of activity of animal life are much

shorter in the infant who fatigues his organs in a few hours, in whom,

consequently, the want of sleep returns oftener, and in whom this

state of intermission of animal life is more profound. It is rare that

infants, in the first months, can pass the whole day awake, especially

if many objects engage them. We might prolong their wakefulness by

removing them from light, sounds, &c.

The multiplicity and frequency of the sensations of the infant, lead

necessarily to a number of motions which have not strength, because

of the weakness of the muscles, but which are, like the sensations,

extremely numerous. As the sight incessantly presents new objects to

the infant, it wishes constantly to touch; its little hands are in

continual agitation, its whole body is also in constant motion. It

is necessary that the nerves which serve to transmit the principle of

these motions, should be adapted by their development, like those of

the sensations, to their constant action.

These two things, the great development of the nervous system and the

frequency of its action in the infant, make the diseases of this system

the predominant ones at that age. So great is the susceptibility of the

brain in answering to sympathetic excitements, that if pains are at all

severe in any part, they immediately produce convulsions, which are at

least four times more frequent at this age than any of the following. I

would observe upon this subject, that the different systems are more or

less disposed in the different ages, to answer to sympathies, according

as their predominance in the economy is more or less decided. The same

morbific cause, fixed upon any organ, which produces convulsions in

an infant by acting sympathetically upon the brain, would give to a

young girl a suppression of the catamenia, by influencing the womb,

which then begins to predominate; to a strong vigorous young man, a

peripneumony; to an adult, in whom the gastric viscera predominate, an

affection of these viscera, &c. It is thus that the same passions that

would give to this one a jaundice, engorgement of the liver, &c. would

produce more particularly in an infant an epilepsy, which attacks the

brain.

The nervous functions are not only frequently deranged by sympathy in

infancy, but it is particularly at this age that the greatest number of

organic diseases is found in the brain, the spinal marrow, the nerves,

or the organs that depend upon them. Cerebral fungi, hydrocephalus,

spina bifida, &c. are a proof of this. The great quantity of blood that

goes at that period to the nervous system has much influence upon this

phenomenon; now this quantity is brought there by the predominance of

the vital forces.

In proportion as the infant grows, its nervous system and the brain,

which is the centre of it, lose by degrees the predominance that

characterize them. Their diseases become less frequent. They are

brought finally to the level of the other systems.

III. _State of the nervous system after growth._

At puberty, the empire of the brain, which is insensibly diminished,

gives place to that of the genital organs, which have a sudden

increase. The cerebral nerves appear to me to have but little influence

upon their development, as well as upon that of most of the other

systems. Observe, in fact, that all the phenomena of generation are

governed by the organic forces, which, as we have seen, are absolutely

independent of the nerves. Thus the great excitement of the genital

organs, from which arise satyriasis, nymphomania, &c. have no analogy

with convulsions whose principle is in the brain; as the destruction

of the venereal appetite is wholly disconnected with the phenomena of

palsies. This is so true, that often during those that affect the lower

half of the body by a fall on the sacrum, or by any other cause, the

secretion of semen and venereal desires take place as usual.

Beyond puberty, and towards the adult age, when the general equilibrium

is more nearly established among the different systems, the nervous is

not affected more than those of which we have had occasion to speak in

treating of this system.

IV. _State of the nervous system in old age._

At this period of life, the nervous cerebral system has but very few

functions to perform. As to sensation, this being almost blunted by

habit, is the reason why external bodies make but little impression

upon the organs of sense; many of these, especially the eye and the

ear, are often shut to sensations before general death. The nerves

have then but little to transmit, and the brain but little to perceive.

As to motion, there is but little in old age, because but little is

felt; for feeling and motion are two things that generally follow the

same proportion. The brain and the nerves are almost inactive in this

respect. The first is not put in action by the intellectual functions;

memory, imagination, judgment, attention, &c. all are enfeebled, none

are exerted with clearness.

Changes of structure constantly accord with these changes of functions.

In the fœtus, the brain is almost fluid; in old age, it is extremely

firm. This organ has passed through a variety of gradations between the

two extreme ages. We know that anatomists always select the brain of an

old person in order to study this viscus, all the parts of which are

broken with difficulty. I would observe upon this subject, that what is

natural at this age, indicates in a young person a morbid alteration.

In general, we have not yet sufficiently studied the comparative

anatomy of the different ages, to make applications of it to the

examination of dead bodies.

The vessels diminish in the brain in proportion as its hardness

increases. In this respect it has an inverse arrangement at the two

extreme ages of life. Its colour becomes more dull in old age. It is

rare that it is ossified; there are, however, some examples of it. The

phenomena, that the action of different re-agents presents, are very

much slower in taking place than in the adult and especially in the

infant. The solution by alkalies is a remarkable proof of this.

We cannot doubt but that this organic state of the brain in old age,

has much influence upon the preceding phenomena; to this must be

referred the less acuteness of pain at this age. A cancerous tumour

of an old person, exactly analogous in its position, form, size and

nature to that of an adult, produces much less suffering. Cancers of

the womb, the stomach, the breast, &c. furnish examples of this. All

the local causes of pain show also the same thing. In the numerous

experiments I have made upon living animals, I have uniformly observed,

that young ones, when the sensible parts are cut, give signs of the

most acute pain; whilst old ones show infinitely less expression of it

under similar circumstances. I would make one other remark upon this

subject; it is that the variety appears in dogs, in a certain degree to

have an influence upon the acuteness of their sensations. All the large

varieties make but little noise, and are not much agitated, when their

skin, their nerves, &c. are cut; whilst all the small ones, though they

may be old, struggle, are agitated, and manifest upon the slightest

cause, the most acute sensibility.

As to the influence of age upon pain, it is not astonishing that the

animal sensibility having become very obscure in a natural state,

should preserve the same character in disease. An old person suffers

then much less than the adult, and especially than the infant, under

the influence of the same causes; it is a compensation for the

diminution of their enjoyments. The infant finds in every thing that

surrounds him, a cause of pleasure or of pain; thus smiles and tears

succeed each other a hundred times a day upon his little face. An old

person on the contrary is always calm; indifference is his natural

state.

The nerves experience the same changes as the brain; they harden

gradually with age; however their proportion of hardness in the

first and last ages is much less remarkable than that of this organ;

this arises from the nervous coat; for the effect upon the medullary

substance appears to be the same. This medullary substance has appeared

to me to be less abundant in the optic nerve of an old person; however

it is difficult to determine the quantity. The colour of the nerves

becomes dull, like that of the brain. They receive fewer vessels. They

are never ossified.

Sometimes we say that the extremities of the nerves have become

callous; it is a vague expression, to which no meaning can be attached.

When will medical language cease to refer to the empty and inaccurate

hypotheses that formerly constituted medicine? Most of these hypotheses

have passed away, yet the names to which they gave birth remain.

The nervous system and the brain frequently lose beforehand, in old

people, a part of their functions; hence hemiplegia is almost as

frequent at that age, as convulsions which are its opposite, are in

infancy. It is necessary to distinguish the hemiplegias of old people

from those of adults. They are of the same nature as the blindness,

the deafness of old people; the difference is only in the injury of

sensation or motion.

NERVOUS SYSTEM OF ORGANIC LIFE.

GENERAL REMARKS.

No anatomist has yet considered the nervous system of the ganglions

in the point of view in which I shall present it. This point of view

consists in describing each ganglion as a distinct centre, independent

of the others in its action, furnishing or receiving particular nerves

as the brain furnishes or receives its own, having nothing in common,

except by anastomoses, with the other analogous organs; so that there

is this remarkable difference between the nervous system of animal

life, and that of organic life, viz. that the first has a single

centre, and that it is to the brain that every kind of sensation comes,

and that it is from it every kind of motion goes; whilst in the second,

there are as many little separate centres, and consequently little

secondary nervous systems, as there are ganglions.

We know that all anatomists, even those who, without affixing to

the expression any very definite meaning, have called the ganglions

little brains, have taken them for dependancies, for enlargements

of the nerves, in whose course they are found; and as most of them

are met with in the great sympathetic, they have presented them as

a distinctive character of this nerve. But from the general idea I

have just given of the ganglions, it is evident that this nerve has

no real existence, and that the continuous thread that is observed

from the neck to the pelvis, is nothing but a succession of nervous

communications, a series of branches that the ganglions placed above

each other, send reciprocally to each other, and not a nerve going from

the brain or the spine.

The first considerations that induced me to think that the great

sympathetic is not a nerve like the others, but a series of

anastomoses, were the following. 1st. These communications are often

interrupted, without any inconvenience, in the organs to which the

great sympathetic goes. There are subjects, for example, in whom is

found a very distinct interval between the pectoral and lumbar portions

of this pretended nerve, which seems cut in this place, because the

last pectoral ganglion and the first lumbar do not send branches to

each other. I have often seen also the sympathetic nerve cease, and

afterwards appear again between two ganglions and from the same cause,

whether in the loins, or in the sacral region. 2d. Every one knows

that the opthalmic ganglion, the spheno-palatine, &c. are constantly

distinct, and that they do not communicate by their branches except

with the cerebral nerves. It uniformly happens that there is between

them and those of the great sympathetic, what we sometimes see between

these last, viz. a complete deficiency of communication. 3d. In birds,

as has been observed by Cuvier, the superior cervical ganglion is also

found constantly distinct; it never communicates with the inferior.

The filament which in quadrupeds descends the length of the neck, is

wanting in them. In many other animals we frequently find interruptions

in this succession of anastomoses of ganglions, which constitute

what is called the great sympathetic. 4th. The communications of the

ganglions are usually made by a single branch; but sometimes many go

from one of these organs to the other, so that if the great sympathetic

was a nerve like the others, it would present, in this respect, an

arrangement wholly different from that of the cerebral nervous system.

5th. Whence does the great sympathetic arise? From the sixth pair? But

all the nerves diminish as they go from the brain towards the organs;

but this presents then an arrangement entirely different; it increases

as it sends off branches. Does it arise from the spinal marrow? But

then the branches with which it furnishes a region would come from the

branches that it receives from the spinal marrow in this region. Thus

the great and small splanchnic would arise from certain intercostal

pairs, now they are evidently much larger, the first especially, than

the sum of the branches from which they would derive their origin.

Observe then that all anatomists have been of a different opinion upon

the origin of the great sympathetic. How could they agree upon a thing

that has no real existence?

These different considerations render probable the opinion that I have

entertained for some time, that the great sympathetic nerve does not

really exist, that this cord is but a succession of communications

between little nervous systems placed above each other, and that it

is not essential that these communications should exist, as is seen

constantly between the ophthalmic ganglion and the spheno-palatine,

between that and the superior cervical, of which many animals furnish

examples. Then I began to regard each ganglion as a separate centre

of a little nervous system, wholly different from the cerebral, and

distinct even from the little nervous systems of the other ganglions.

By considering the functions of the nerves going from these centres, I

became more and more convinced that they did not belong to the cerebral

system. In fact, these nerves have properties very different from

theirs, as we shall see; they do not serve for sensations; they have

uniformly no connexion with voluntary locomotion; we see them only in

the organs of internal life; hence why they are found concentrated in

the trunk, in the thorax and abdomen particularly; why they are not

met with in the head, where almost all the organs belong to animal

life; why they are not seen in the extremities, which are exclusively

dependant upon this life.

Distributed almost every where to the organs of the internal life,

the ganglions and their nerves derive their character from it; and

this is it. 1st. They are not symmetrical; thus the nerves of all the

plexuses of the abdomen, those of the cardiacs, &c. have a remarkable

irregularity. 2d. There are numberless varieties in the form of these

plexuses and in that of the ganglions; it is thus that, sometimes

lenticular, sometimes triangular, sometimes divided into many portions,

that which is under the diaphragm is never seen twice alike. Hence

the error of every name derived from the figure; a remark that is

applicable generally to the organs of internal life. We might rather

borrow the names of forms for animal life in which these forms are more

invariable. On the other hand, the existence of many ganglions varies;

sometimes there are three of them in the neck, at others but two. The

arrangement of one side does not produce a similar one on the other.

I have frequently remarked that the number of filaments arising from

the superior cervical ganglion differs very much from those that take

their origin from the opposite side. There are two analogous organs

at each side; but several attributes of structure destroy the general

character of symmetry; it is like the lungs and the kidnies. We can,

then, establish as a distinctive character between the two nervous

systems, the symmetry of one and the irregularity of the other; now,

this character is one of those which distinguish the two lives, as I

have remarked before.

From all this it is evident that a line of demarcation separates the

nerves of the ganglions and those of the brain, and that the method

is inaccurate which considers them as forming a single nerve, arising

by some origin from this last. Their communications no more prove it

to be a general nerve, than the branches which pass from each of the

cervical, lumbar, or sacral pairs, to the two pairs that are superior

or inferior to it. Notwithstanding these communications, we consider

each pair in a separate manner, and not as one nerve by their union. So

that each ganglion should be described separately, notwithstanding the

branches it sends to others.

The description of the system of the ganglions should be analogous

to that of the cerebral nerves. For example, I describe first the

lenticular ganglion, as was done for the brain; then I examine its

branches, among which is found the great splanchnic; for it is very

improper to say that this nerve gives origin to this ganglion. The same

in the neck, in the head, &c. each ganglion is first described; then I

treat of its branches, among which are found those of communication.

There are, then, almost as many descriptions as there are separate

ganglions. For example, we ought not to treat of the ophthalmic nerve

with the common motor; to be convinced of this, it is sufficient to see

how much the ciliary nerves differ from the others, which, belonging to

animal life, are also contained in the orbit.

From all that has been said, it is evident that there are two things to

be examined in the nervous system of organic life, 1st. the ganglions;

2d. the nerves that go from them.

ARTICLE FIRST.

OF THE GANGLIONS.

I. _Situation, forms, relations, &c._

The ganglions are little reddish or greyish bodies, situated in

different parts of the body, and forming so many centres, from which

goes an infinite number of nervous ramifications. Their position most

generally is along the vertebral column, where are seen successively

below each other, the superior and inferior cervical, the intercostal,

the lumbar, and the sacral. It is these especially whose communicating

branches form the great sympathetic. But besides these ganglions, which

are placed as it were in a row, we find many separate ones in different

parts, as the ophthalmics, the sphenopalatines, the maxillaries in the

head, as also the semilunars in the abdomen. In the thorax there are

none thus separate; though sometimes we see a small one at the base of

the heart.

Besides the ganglions uniformly seen, there are often accidental

ones, if we may so say; such are those that are sometimes found in

the hypogastric plexus, in the solar even, at some distance from the

semilunar, in the middle part of the neck, &c. On the other hand, some

of those that are usually met with are oftentimes not found, as some of

the lumbar, sacral, maxillary, &c.; so that it appears that there is

really an essential difference between the ganglions under the relation

of existence. The superior cervical, the semilunar, the ophthalmic, &c.

are always found; they appear to be essentially necessary to the action

of the organs to which they furnish nerves. Most of the others may be

wanting on the contrary, and be supplied by those of the neighbouring

ones, or by others formed not in the ordinary anatomical order.

All the ganglions are generally in a deep situation. Destitute of

a bony covering analogous to that of the brain, they are not less

powerfully protected against the action of external bodies. It is this

deep position, that prevents us from making experiments upon almost

all of them, from making those at least which require that the animal

should live a certain time after they have been made. It is this which

will undoubtedly keep up for a length of time the obscurity that hangs

over the functions of these organs.

The form of the ganglions is extremely irregular. In general they are

round; but sometimes they are long, as the superior cervical; sometimes

the ganglion is a species of triangular body, with obtuse and round

ends, as the ophthalmic; sometimes the form is semilunar, like that

which has this name, &c. Generally these forms are very variable, as I

have said; the most uniform is that of the superior cervical.

Embedded in a quantity of cellular texture, all the ganglions are

separated by it from the neighbouring organs. Almost all of them

are so disposed, that they experience but little motion from these

organs, and cannot receive it from any of the vessels that enter them.

Those situated along the vertebral column especially, present this

phenomenon, very different from that which takes place at the brain,

whose functions are essentially connected with the constant agitation

that the blood imparts to it, and very different from that which we

observe in the plexuses of nerves coming from these same ganglions.

II. _Organization._

The ganglions have generally in the adult a reddish colour very

different from that of the nerves; sometimes they are greyish. When

opened, they present a soft, spongy texture, resembling considerably at

first view that of the pretended lymphatic glands.

This texture has nothing in common with the cerebral substance, nor

with that which occupies the canal of the nervous coat. These two

last should rather be ranked in the class of fluids, as I have said;

their substance is a pulp, a real jelly. Thus they have not any of

the properties of solids. They do not harden like horn; the kind of

hardening, the result of the contact of alkohol, of the acids, and of

caloric, is wholly different from the horny hardening. It is analogous

to the hardening of the white of an egg. On the contrary, the texture

of the ganglions hardens like horn in an evident manner, a phenomenon

which is characteristic of all the solids, except the epidermis, the

nails, and the hair, which make a separate class. Treated by the acids,

the ganglions, after wrinkling, hardening like horn and hardening

gradually, soften and become fluid.

Boiling produces a phenomenon nearly analogous; 1st. horny hardening

and hardening at the instant the water boils; 2d. continuance of this

state for half an hour; 3d. softening gradually brought on; when this

last is complete, the effect of the boiling is finished. In this state,

the ganglions are all different from the nerves submitted to the

same experiment. I have observed also in veal, that they have a very

different taste from that of the nerves, a method of research which

should not be neglected in attempting to ascertain the difference of

the nature of the organs. In fact, as we do not yet know the difference

of the principles which enter into the composition of each, we should

be satisfied with the difference of the qualities.

The alkalies act a little upon the ganglions, which they tend to

dissolve, and which they do partly dissolve, if they are very caustic.

But this solution is infinitely less prompt and less easy than that

of the cerebral pulp by the same re-agents. The ganglions resist

putrefaction as much and even more than the nerves; this forms also a

very remarkable difference between them and the cerebral substance. In

general, we cannot establish any kind of analogy between them.

The texture of the ganglions appears in nowise fibrous; there is

absolutely no linear, filamentous appearance, &c. upon simple

inspection. Homogeneous, if we may so say, in its nature, it presents

every where an uniform aspect when cut in slices. However the

celebrated Scarpa has considered the ganglions as resulting from a

kind of expansion of the nerves, into an infinite number of extremely

delicate fibres, which interlace with each other, and which become

very distinct by maceration. I have not repeated all his experiments,

which appear to me extremely difficult. I refer then to his work, and

to the plates it contains. I would observe only that there is certainly

something else in the ganglions, besides a simple division of the nerve

into extremely fine threads. In fact, mere inspection is sufficient to

establish between them the greatest difference. There is as evident a

demarcation between the ganglions and the nerves, as between those of

the brain and the brain itself. 1st. Difference of colour, reddish or

greyish tinge in some, white in others; 2d. difference of consistence,

of external qualities, &c.; 3d. difference of properties. If the nerves

coming from the spinal marrow make only an expansion, in their passage,

in the ganglions, by delicate filaments, there would then be only a

difference of form and not of nature; the properties would be the same.

Why then are they so different as I shall prove hereafter? Why, as a

nerve goes from a ganglion, does it not communicate more voluntary

motions? 4th. Why has not nature placed ganglions in the nerves of the

extremities as in those of the other parts? If there is only a division

of the nerve into finer filaments, in the ganglion, why is there not a

proportion between the filaments that enter on one side, and those that

go out at the opposite? In fact, those that enter into the superior

cervical above, if they only expanded their filaments in this ganglion,

and united afterwards to form those that go off below, would be equal

in respect to size to those that go from it; all the ganglions would

exhibit this constant relation between the nerves of one side and those

of the opposite; now, it is sufficient to examine them to be convinced

that an inverse arrangement exists. 6th. The ganglions ought always to

be in proportion to the size of the nerves which form them by spreading

their fibres. Why then are the intercostal ganglions so small, and the

trunks that unite them, or rather that give origin to them and which

go from them afterwards as we see in the usual manner, so large? Why

on the contrary, is the superior cervical ganglion so large, and its

branches so small? 7th. How can be explained the frequent interruptions

between the ganglions in man, which are constant in many animals, if

there is a continuity between the nervous filaments that enter the

ganglions above, and those that go from them below? 8th. How does it

happen that the ganglions and their nerves do not follow an exact

proportion as to development with the cerebral nerves, if these form

them by expanding? 9th. Why has not pain the same character in each

species of nerves?

I have no opinion as to the nature or the functions of the ganglions,

because I have no fact to support me; but there is certainly something

more in their texture, than a mere expansion of nervous filaments.

Scarpa admits a peculiar matter which separates these filaments; but

this substance ought to predominate considerably, as the ganglion

surpasses in size the nerves which are thought to give origin to it.

Now I have never seen this substance; I do not know what it is; all is

solid when the ganglion is cut. I think then by admitting, even to a

certain extent, the internal arrangement that this author has observed

in the ganglions, we cannot describe these organs in the point of view

in which he has presented them.

We know but little of the alterations that diseases produce in the

texture of the ganglions. I have already many times examined in

diseases of the heart, of the liver, of the stomach, the intestines,

the ganglions that send nerves to these viscera; they have never

appeared to me to have undergone any change. In cancers of the stomach

in the very last stage, in which all the cellular texture is engorged,

and in which all the lymphatic glands are considerably swelled, I have

always found the semi-lunar ganglion untouched, except however in one

case where it was enlarged and its density a little increased. At

another time I found this same ganglion of the size of a small nut,

with a cartilaginous substance in its centre, resembling the stone

of it, in the body of a man brought to the Hôtel Dieu on account of

periodical mania. Some authors have thought, and I suspect the same

thing also, that the hysteric paroxysms, which begin by a contraction

at the epigastric region, and in which the patient feels a ball mount

up even to the throat, arise from some affections of the semi-lunar

ganglions, from the solar plexus and the communications which go from

ganglion to ganglion, even to the neck. However two bodies that I have

opened lately, exhibited no alteration, though during life the subjects

had been frequently attacked with these paroxysms; but they may arise

evidently from the ganglions and the epigastric plexuses, without their

being altered in their structure, as a number of cerebral affections

leave after them no trace in the brain. This point deserves particular

examination.

It does not appear that the texture of the ganglions is surrounded

by a peculiar membrane. The cellular texture is only condensed in

their neighbourhood; it then becomes very consistent, and much

contracted around them. It there has the nature of the sub-mucous,

the sub-arterial textures, &c.; it never contains fat. There is then

truly around the ganglions, as around the arteries, under the mucous

surfaces, &c. the two kinds of cellular texture of which we have

spoken in treating of the organization of this texture, and which

differ so essentially from each other in their nature, and even in

their properties. It is the second kind, which is analogous to the

sub-arterial texture, &c. which forms the peculiar membrane admitted by

some authors.

By examining attentively the interior of the ganglions, we see that

there is but very little cellular texture there. I have found this

texture constantly destitute of fat; thus the alkalies do not form a

saponaceous deposit upon them, as upon the cerebral nerves when plunged

in their solution. I have examined many ganglions in this way, on

account of the opinion of Scarpa, who believes that these organs are

penetrated with this fluid, at least in fat people.

The ganglions receive many blood vessels. These penetrate them from

all sides, run first in a kind of cellular covering that surrounds

them, then entering their texture, ramify and are lost there in

numerous anastomoses, and in continuation with the exhalants that carry

nutritive matter. Fine injections show a great quantity of vessels in

these little organs. Nutrition supposes exhalants and absorbents there.

III. _Properties._

It is difficult to analyze the properties of texture in the ganglions.

As to vital properties, they cannot grow, live and be nourished

without organic sensibility, and without insensible contractility

of the same kind. Animal and sensible organic contractility do not

exist there evidently. As to animal sensibility I have observed the

following circumstance. As in opening the abdomen of an animal, of a

dog, for example, he lives very well for some time, and remains even

calm after the first moments of suffering; I have waited for this calm

that succeeds the agitation arising from the incision of the abdominal

parietes, then laid the semi-lunar ganglion bare, and irritated it

powerfully; the animal is not agitated, whilst when I excite a cerebral

lumbar nerve, for comparison, he cries out, raises himself up and

struggles. In general it appears that the sensibility of the ganglions

is infinitely less evident than that of many other organs. Certainly

the skin, the mucous system, the medullary, the nervous of animal life,

&c. surpass it in this respect.

Our ignorance as to the diseases that have their seat in the ganglions,

the distance of those organs from external excitement, prevent our

having any data as to their sympathies. I think it very probable,

however, that these sympathies take a real part in hysteria, in

certain kinds of epilepsy, the paroxysms of which begin, like those

of hysteria, by a painful sensation at the epigastric region, in

that multitude of affections called nervous, and which the vulgar

confound under the name of vapours. One of the most important objects

of research in the neuroses, is to determine those that have their

particular seat in the nervous cerebral system and those which

affect more particularly the system of the ganglions. Place on one

side, palsy, hemiplegia, convulsions of infants, tetanus, catalepsy,

apoplexy, the greatest part of epilepsies, all the numerous accidents

that arise from engorgements, from compressions of the brain from

wounds of the head, nervous affections of the sight, hearing, taste,

smell, &c. and all the diseases the source of which is evidently in

the head; on the other place hysteria, hypochondriasis, melancholia

and all that numerous class of affections in which the abdomen and the

thorax, the first especially, seem to be the spot in which the evil is

seated; you will see that there is an essential difference and that

the symptoms have entirely a different character. I do not say that

the last kind of nervous diseases affect exclusively the ganglions;

for too much obscurity hangs over these affections to pronounce any

thing positive as to their seat, or their nature. Undoubtedly even the

secretory, circulating, pulmonary organs, &c. can be then particularly

affected in their peculiar texture and independently of the nerves they

receive; but certainly it is an interesting subject of research, and

there is too great a difference in the phenomena of the two orders of

affections, not to present differences in their primitive seat. It is

difficult to conceive that the system of the ganglions has not a great

part in the last order.

That which induces me to think that the difference of the phenomena

that the general order of neuroses presents us, arises particularly

from the difference of the cerebral nerves and of those of the

ganglions, is that their phenomena in a state of health are very

different. Hallé has observed very well that the pains that are

experienced in the parts in which the nerves coming from the ganglions

are distributed, have a peculiar character, and that they do not

resemble those that are felt in the parts where the cerebral nerves

are sent. Thus the painful sensation that is experienced at the loins

in affections of the womb, by vinous injection made into the tunica

vaginalis, &c. a sensation that appears to me to arise from the

sympathetic influence exercised by the organ affected upon the lumbar

ganglions, the pains of the intestines, the burnings at the epigastric

region, &c. &c. do not resemble pains of the external parts; they are

deep, and go to the heart, as we often say. We know that there are

colics essentially nervous, which are certainly independent of every

local affection of the serous, mucous, and muscular systems of the

intestines. These colics are evidently seated in the nerves of the

semi-lunar ganglions, which are spread along the whole course of the

abdominal arteries. They are real neuralgias of the nervous system of

organic life; now these neuralgias have absolutely nothing in common

with the tic douloureux, sciatica, and other neuralgias of the nervous

system of animal life. The symptoms, the progress, the duration, &c.

every thing is different in these two kinds of affections.

What I have just said upon the injuries of sensation, applies also

to those of motion. No kind of comparison can be made between the

convulsions of the muscles that receive the nerves of animal life, and

the spasmodic and irregular motions which arise in all the muscles that

receive nerves from the ganglions. Nothing resembles tetanus in the

heart, the intestines, the bladder, &c.

All these considerations establish striking differences between the

cerebral nerves and those of the ganglions; differences upon which I

can only present approximations, as we have no data as to the functions

of the last.

IV. _Development._

The ganglions differ essentially from the brain in the early periods

in their development, which is proportionably much less advanced than

that of the brain. They are only on a level with all the other organs,

whilst this is infinitely superior to them in this respect, as we

have seen. By comparing the superior cervical, semilunar ganglions,

&c. in the fœtus, and in the adult, it is easy to make this remark.

The ganglions receive also less vessels in proportion than the brain.

They do not follow the proportion of increase of the organs to which

they send nerves. Thus those that furnish the genital organs, which

are nearly nothing during the first years of general nutrition, are as

large in proportion as those which go to the liver, the stomach, the

intestines, which are characterized by an early increase. These nerves

follow in this respect the same law as the ganglions, though the most

are found upon the arteries, which are more or less developed according

to the organs they penetrate.