The nervous system of organic life being less early in its development

than that of animal life, should be subject in infancy to fewer

affections; and this is what is observed. Convulsions, and most of the

neuroses of the second, are, as we have seen, a peculiar appendage

upon infancy. On the other hand, the particular order of nervous

affections of which we have spoken, and in which it appears that the

first takes the principal part, is generally less frequent at this

period. All nervous diseases, whose peculiar seat seems to be at the

epigastric region, in which there is so great an abundance of nerves

coming from the ganglions, appear to be foreign to this age.

Another difference that distinguishes the ganglions from the brain as

it respects development, is this, that in the fœtus, they are not, like

it, of extreme softness. Their hardness is little inferior to what they

afterwards possess in adult age.

In proportion as we advance from infancy, the organic nervous system

begins to become predominant. It is towards the thirtieth or fortieth

year that it appears at its maximum of action; it diminishes as we

approach old age; it decays in part at this epoch. The nerves become

greyish; the ganglions are hard, resisting and smaller. The neuroses

that appear to belong to them are infinitely more rare. Moreover, the

obscurity that rests upon the functions of this system, does not allow

me to point out definitely the alterations they experience in the

different ages.

V. _Remarks upon the vertebral ganglions._

In all that I have said thus far upon the ganglions, I have not noticed

those which correspond with the foramina through which the nerves pass,

and which some call simple ganglions. We know that at the instant

each nerve goes from each of these foramina, it exhibits an evident

enlargement, reddish, pulpy, analogous in its appearance to most of

the ganglions. I confess, that I know not how to class these organs.

We cannot deny that they have the greatest analogy in structure to the

others. They are approximated in another respect, which is this, that

the nerves, in going from them, form almost immediately plexuses that

we have designated under the names of cervical, brachial, lumbar, and

sacral, in the same way as the solar, cardiac, mesenteric plexuses, &c.

are formed by the nerves of organic life, at the moment they go from

their respective ganglions. However, these last nerves are conductors

of very different properties. Irritate in a living animal the superior

cervical ganglion, the inferior even, which is more difficult, though

it may be come at, the muscles to which they send nerves will remain

unmoved; the same phenomenon takes place by exciting the nerves

themselves. On the contrary, every irritation of a filament coming

from the vertebral ganglions, produces immediately convulsions in the

corresponding muscles. The sensibility is entirely different in the two

species of nerves. Besides, there is no analogy between the manner in

which the nerves go in all directions from the vertebral ganglions, and

that in which the other ganglions furnish theirs. In the expectation

that further experiments may elucidate the subject, let us content

ourselves with pointing out what is the result of accurate observation.

ARTICLE SECOND.

OF THE NERVES OF ORGANIC LIFE.

I. _Origin._

Each ganglion is, as we have seen, a centre from which go in different

directions, various branches, the whole of which form a kind of little

separate nervous system. The manner of the origin of these branches has

but very little relation with that of the branches of the brain and of

the spinal marrow. The following are some differences that distinguish

it.

1st. The adhesion is much stronger; the nerve breaks any where else

rather than at its origin; the opposite of this takes place in the

preceding system. 2d. It does not appear that the substance of the

ganglion is continued in the nerve to form the medullary substance of

it, since the organization of the one and the other is very different.

Sometimes, however, the ganglion is continued for a short distance in

the form of a cord. This happens especially in the superior cervical,

in the lumbar, the semi-lunar, &c. Then the form only is different; but

it is easy at the first view to distinguish where the ganglion ends

and the nerve begins. 3d. This beginning is made in a sudden manner;

it is like a muscle implanted in a tendon. The best manner of seeing

this arrangement to advantage is to cut longitudinally the superior

cervical ganglion and the cord it sends to the inferior; the change

of nature of the one and the other is then very apparent; or, if we

consider the ganglion as a division of the numerous filaments of the

nervous cords, we distinguish very well the sudden change that these

filaments experience in passing from the cord to the nerve. 4th. The

dense cellular covering that surrounds the ganglion is continued upon

the nervous origin, and gives it an increase of consistence at that

place. This must be carefully raised before we come to the nerve. We

see then each distinct filament arising from the ganglion. After it has

gone from it, sometimes it remains separate; this takes place at the

semi-lunar, the lumbar, the opthalmic, whose elongations are of great

delicacy. Sometimes many of these filaments unite together and form a

cord as between the two cervical, as at the great and small splanchnic

nerves, &c.

I have not been able by maceration, ebullition, or the action of the

acids to destroy the adhesion of the nerve with the ganglion, as we

destroy that of the muscle with the tendon, of this with the bone, &c.

II. _Course, Termination, Plexuses._

The nerves after going from the ganglions, are distributed in many

different ways which we shall now examine.

1st. There are always some which go immediately to communicate with

the system of animal life. The ophthalmic ganglion sends branches to

the motores communes, and to the nasal nerve. The spheno-palatine

communicates with the superior maxillary nerve; the superior cervical

with all the nerves that surround it, viz. above with the motor

externus, within with the great hypoglossal, the par vagum, the

glosso-pharyngeal, the spinal, &c.; behind with the first cervical

pairs. All the ganglions situated above each other along the vertebral

column, send communications through each pair of foramina that

correspond with them. The par vagum communicates with the semi-lunar,

&c. It is not then any separate ganglion of the nerves of animal

life; hence the common expression that designates each ganglion as

arising from this or that pair, or being found in its course, is very

inaccurate. Thus the opthalmic is by no means in the course of the

common motor nerve. The one and the other send each a branch, which

unites; or rather there is a branch of communication between the

ganglion and the cerebral nerve. In general all these branches of

communication with the system of animal life, are short, whitish, and

of the same nature, or at least of the same appearance as the nerves of

this last. They do not form any plexus in their course, rarely furnish

branches, and appear to have no other use than that of establishing

anastomoses between the two systems.

2d. Each ganglion sends above and below branches to the two ganglions

that are contiguous to it. We have seen that the opthalmic and the

spheno-palatine are exceptions to this rule. Sometimes also, as I

have said, there are interruptions in other regions. Notwithstanding

this, these general communications make us regard the ganglions as

being connected every where, and able to receive from each other the

different affections of which they can be primitively the separate

seat. These branches of communication are straight as in the preceding,

sometimes very fine, as between the lumbar and sacral ganglions, at

other times larger, as that which is between the two cervical, superior

and inferior, in some cases very large, as the great splanchnic,

which is a real trunk of communication between the intercostals and

the semi-lunar. The nerves that we are now considering, the last

especially, have like the preceding, an arrangement exactly analogous

to the cerebral nerves; they are formed of whitish cords, which are the

result of filaments. The eye discovers no difference between them.

3d. Many filaments coming from ganglions, go to certain cerebral

muscles, as to the diaphragm, some of those of the neck, &c.; others go

to neighbouring organs only.

4th. The greatest number going from the ganglions in separate

filaments, interlace in the form of a plexus with those of the

contiguous ganglions, in the neighbourhood of, or upon the great

vessels. The most remarkable plexus is the solar, composed by the

innumerable branches that come from the semi-lunar; then we see the

hypogastric, the cardiac, &c. The greater number of these plexuses are

not exclusively formed by the nerves of organic life; those of the

animal give some to them also, as the par vagum furnishes an example

for the solar and the cardiac, as the sacral nerves afford another

for the hypogastric, &c. However the nerves of organic life always

predominate in these plexuses. There is only the pulmonary in which the

par vagum particularly predominates, whilst the nerves coming from the

inferior cervical ganglion are, if we may so say, but accessory.

The primitive plexuses resulting from the interlacing of the organic

nerves at their exit from the ganglions, form a mass of irregular

nerves, buried in the cellular texture, accommodated to the forms of

the neighbouring organs, and wholly different from those of animal

life, as of the brachial, the lumbar, &c.

In fact, the filaments at every instant, not only place themselves as

in the preceding ones, at the side of each other, at every change of

position; but their extremities continue; they interlace with each

other, change at every point the direction, form networks, and mix so

together, that it is not possible to distinguish any thing except a

thousand nerves, that we might say grew up under the cloth with which

we wiped the place where the plexus was found.

These organs are remarkable for their reddish or greyish colour, for

their softness, for their indistinctness, &c.; it is often difficult

to distinguish them from cellular texture. The best manner of making

them evident is to let the subject macerate for a day or two open in

the water; they whiten then sensibly, do not soften, and appear even to

increase in consistence, like the cerebral nerves in a similar case.

Besides their delicacy is such, that it is impossible to submit them

to any kind of reagents. Only I have observed that they possess in an

eminent degree the property of horny hardening, and that they do not

yield in this respect to the cerebral. This delicacy depends upon this,

that all the filaments are separate from each other, instead of being

like the preceding, collected into cords; it is this also that makes

these nerves so numerous. If all the filaments of the brachial plexus

were separated like those of the solar, they would present the same

appearance and the same number in their interlacing.

Do the primitive plexuses formed by the ganglions perform a part in the

nervous functions? are they centres to which are referred important

phenomena? What has not been said upon this subject, concerning the

solar plexus? But nothing, I believe, of all that has been advanced is

founded upon accurate observation.

The plexuses of organic life are soon separated into different

divisions, which go to different parts, to those especially of this

life. These divisions arise from an infinite number of little filaments

which go constantly separate, though placed near each other, and which

never unite into cords like the preceding. They accompany almost all

the arteries; thus the renal, the hepatic, the splenic, the coronary

stomachic, the mesenterics, the hypogastric, the carotid and its

distributions, &c. are surrounded with filaments coming from ganglions.

These filaments go in two ways. 1st. Some accompany the artery without

being connected with it; considerable cellular texture separates them;

they go in its course without intermixing in a sensible manner with

it. 2d. The others form for it, if we may so say, a new coat, exterior

to the others, which adhere to it intimately, and which interlace so

together, that they might be taken for a network surrounding the artery.

When the artery runs but a short course, these two orders of branches

remain distinct from each other as far as the organ, as we see

around the splenic, the hepatic, the renal, &c.; but if the course

is longer, the external branches gradually get into the plexus, and

are entirely lost there. This plexus can be followed upon the great

trunks; it divides upon each branch, and can be still seen; but such

is its tenuity upon the minute ramifications that it disappears there

entirely. The spermatic is one of the arteries upon which it can be

traced the longest. The arteries of the extremities appear to be

destitute of it. In general it is upon those that go to the central

organs of internal life, that this network is the most evident. When

we deduct from the sum of the filaments coming from the ganglions,

those by which they communicate on one part with each other, and on

the other with the nerves of animal life, we see that almost all the

rest is finally destined to accompany the arteries. This arrangement

is wholly different from that of the cerebral nerves, whose filaments

are only in apposition with the vessels. These make almost an integrant

part of them, the adhesion is so intimate; this certainly supposes

a use of which we are ignorant, relative to the circulation, or to

the other organic functions. As these vessels distribute every where

the materials of these functions, of the secretions, exhalations,

nutrition, &c. the organic nerves have no doubt some influence upon

them. Neither experiment or observation have taught us any thing upon

this point.

The veins are not accompanied by so many organic nerves. It is the

same as it respects the absorbent trunks, which go almost every where

separate from this system.

The constant union of the arteries with the organic plexuses, an

union that presents an arrangement wholly different from that of the

ganglions, has undoubtedly an influence upon the action of these

plexuses, or rather upon that of the nerves that go from them, by the

motion the blood communicates to them. It should be remarked upon this

subject, that as nature has placed a crowd of arteries at the base of

the brain to agitate it with an alternate motion, she has put also the

most considerable plexus of the whole organic system upon one of the

places to which the red blood communicates the strongest impulse, viz.

upon the trunk of the cœliac.

III. _Structure, Properties, &c._

From what has been said above, it is evident that the nerves going from

the ganglions are of two sorts as it respects organization; 1st. those

that are identified with the cerebral system, by their white colour,

by the possibility of dividing their trunks into distinct cords, and

these into filaments, which appear to have nervous coats and medullary

substance like the preceding; 2d. those which present only little

separate filaments, greyish or reddish, soft, and which are seen in

prodigious numbers in the plexuses. Have these a nervous coat and a

medullary substance? It is impossible to determine it.

The properties of texture are ascertained with difficulty in the

organic nerves. As to vital properties, it is undoubted that the animal

sensibility is not as much raised in these nerves as in those of animal

life. I have often laid bare the plexuses in the abdomen; then by

letting the animal rest a moment, and by irritating them comparatively

with the lumbar nerves, I have uniformly made this remark. We know that

very frequently the ligature of the spermatic artery is not painful in

sarcocele, though the branches coming from the ganglions form for it

a plexus like a network, which can in no way be separated from it. If

we draw out a portion of intestines by a small wound in the abdomen,

the irritation of the sub-mucous layer at the side of the vessels,

is hardly felt, though many nerves of ganglions are found at this

place. I have had numerous occasions to act in different ways upon the

carotid, to which the superior cervical ganglion furnishes branches

from above; now, as long as I did not touch the par vagum, the animal

remained tranquil. I am far, however, from believing in the absolute

insensibility of the nerves of the ganglions; but certainly under the

circumstances that I have related, the cerebral nerves would have

caused much more pain to the animal.

I think that in a morbid state this sensibility is susceptible of being

greatly raised. We certainly cannot deny but that the solar plexus

takes a great part in the different sensations that are experienced

at the epigastric region; the very acute pains that often attend the

formation of aneurisms, are probably owing in part to the distension

of the nervous filaments that surround the artery. I have already said

that it is probable that the organic nerves are much concerned in the

different sensations that are produced by some peculiar neuroses.

These nerves occasion evident sympathies in certain cases. It is to

this that must be referred the different affections that Petit de Namur

has produced in the organ of sight, by irritating their branches that

are accessible. The development of the nerves of the ganglions follows

nearly the same laws as that of those organs from which they emanate.

Let us observe in finishing this system, that there is no one that

ought to arrest the attention of physiologists more. All the others

present a series of phenomena already well known. Of this, we have

hardly any knowledge. It does not present as yet, if we may so say,

but some of the negative attributes of the nervous system of animal

life. Thus it is without doubt that the organic nerves do not have the

same part as the preceding in animal sensibility; that they are always

foreign to contractility of the same species; that they have no direct

influence upon the sensible organic, since as we shall see, we can cut

or irritate them without destroying or hastening the motion of the

muscles to which they go. But in knowing the parts they do not perform

we are ignorant of those to which they are really destined. I have

already observed that the difficulty of making experiments upon the

ganglions and the plexuses, will much retard the progress of science.

We have scarcely any branches upon the exterior upon which we can act.

Scarpa has collected the opinions of all who have preceded him,

together with his own, upon the uses of the ganglions. I refer to what

he has said upon this subject. As the general point of view in which

he has presented these organs, and that in which I offer them here,

differ essentially, the account that I have just given of the nerves

of organic life has necessarily a general stamp wholly different from

that of his work, a work, however, which, like all this author has

published, confers the greatest honour upon the state of anatomy at the

period in which we live.

I will terminate this article by an important reflection. If the nerves

were only divided to form the ganglions, if these presented in their

interior only differences of forms, and a very minute division of their

filaments, why should they be so constant in animals? Many organs are

wanting, vary, are presented under a thousand various forms in their

different classes; on the contrary, the ganglions are constant. In

those species even in which the cerebral system is imperfect, that of

the ganglions is complete in its organization. Animal life diminishes

and is contracted in an evident manner in most insects, in worms,

&c. and generally in animals without verterbræ. The brain and the

nerves become less evidently marked in proportion as this life is less

perfect. The organic is, on the contrary, almost in its perfection in

these animals. The ganglions and their nerves are also very evident.

This remark has struck me in reading the researches of different

authors upon the anatomy of the lower classes of animals; now, if

the ganglions were not the centres of certain important functions

of which we are ignorant, would they be so invariable in the animal

organization?

VASCULAR SYSTEM

WITH RED BLOOD.

ARTICLE FIRST.

GENERAL REMARKS UPON THE CIRCULATION.

All authors have considered the circulation in the same way, since the

celebrated discovery of Harvey. They have divided this function into

two; one has been called the great circulation, the other, the small or

pulmonary. The heart, being between the two, is their common centre.

But in presenting in this point of view the course of the blood, it

is difficult at first sight to perceive the general object of its

course in our organs. The method in which I explain in my lectures this

important phenomenon of the living economy, appears to me infinitely

better calculated to give a great idea of it.

I. _Division of the circulation._

I divide the circulation also into two; one carries the blood from

the lungs to all the parts; the other brings it from all parts to the

lungs. The first is the circulation of red blood, the second that of

black.

_Circulation of red blood._

The circulation of the red blood commences in the capillary system

of the lungs, where the blood acquires, by the mixture of the

principles that it draws from the air,[6] the peculiar character that

distinguishes it from the black blood. From this system it passes into

the first divisions, then into the trunks of the pulmonary veins; these

pour it into the left auricle of the heart, which transmits it to the

ventricle, and this drives it into the arterial system; this spreads

it into the general capillary system, which may be truly considered as

the termination of its course. The red blood is then constantly carried

from the capillary system of the lungs to the general capillary system.

The cavities that contain it are all lined with a continuous membrane;

this membrane spread upon the pulmonary veins, upon the left cavities

of the heart and upon the whole arterial system, may be considered as

a general and continuous canal, the exterior of which is strengthened

in the pulmonary veins by a loose membrane, in the heart by a fleshy

surface, which is delicate in the auricle, thick in the ventricle, and

in the arterial system by a fibrous layer of a peculiar nature. In

these varieties of the organs that are thus added to it without, this

membrane remains every where nearly the same, as we shall see.

[6] It may be remarked, that this work was published at a time when

the theory of the oxygenation of the blood was universally considered

as explaining in a satisfactory manner the change that is effected

in the colour of the blood by the lungs. The experiments of Allen,

Pepys, and others, and the Treatises of Ellis, have proved to the

satisfaction of most physiologists of the present day, that this

change in the colour is not owing to the absorption of oxygen by the

blood, but to the extrication of carbon from it. _Tr._

_Circulation of the black blood._

The circulation of the black blood is performed in a manner the reverse

of the preceding. It begins in the general capillary system; it is

in this system, that its blood takes the peculiar character that

distinguishes it from the preceding; it is here that it is formed, by

the subtraction probably of the principles of the air that it acquired

by terminating its course in the lungs. From this general capillary

system, it enters the veins which transmit it to the right cavities

of the heart, which send it by the pulmonary artery, to the capillary

system of the lungs. This system is its real termination, as it is the

commencement of the circulation of the red blood. A general membrane,

every where continued, lines the whole course of the black blood,

and forms for it also a general and continuous canal, in which it is

constantly carried from all parts to the interior of the lungs. At the

exterior of this great canal, nature has placed a loose membrane in the

veins, fleshy fibres in the heart, and a peculiar fibrous texture in

the pulmonary artery; but, like the preceding canal, it remains always

nearly uniform, notwithstanding this difference of organs to which it

is united externally. It is by the folds of this membrane in the veins

that the valves are formed. It contributes to form all those of the

right side of the heart, whose cavities it lines, as the preceding

enters into the composition of the valves of the left side, which

borrows from it the membrane that lines it.

_Difference of the two circulations._

From the general idea that I have given of the two circulations, it

is evident that they are perfectly independent of each other, except

at their origin and termination, where the red and black blood are

alternately transformed into each other, and communicate for this

purpose by the capillary vessels. In their whole course they are

entirely separate. Though the two portions of the heart are united

in one single organ, they may however be considered as uniformly

independent in their action. There are truly two hearts, a right and

a left. Both would be able perhaps to perform their functions as well

if they were separate, as they now do united. When the foramen ovale

remains open after birth, I have proved elsewhere that such is the

arrangement of the two folds between which it is found, that the black

blood cannot communicate with the red, and that the two hearts should

equally be considered independent, at least as it respects the course

of the blood. This entire separation of the two circulations is one of

their most striking characters; it alone proves how much preferable the

point of view in which I have presented the circulation, is to that

which divides it into great and small, which are evidently confounded

and identified.

From what has been said, it appears that the origin and termination of

each circulation take place in the two capillary systems, which are, if

we may so say, the limits between which the two kinds of blood move.

The lungs alone correspond in this respect, with all the parts. Their

capillary system is in opposition to that of all the other organs, if

we except the parts from which the blood of the vena porta goes. Each

capillary system then is at the same time an origin and termination.

The pulmonary is the origin of the circulation of the red blood, and

the termination of that of the black. The general gives to the red

blood its termination, and to the black blood its origin. Observe that

this is a great character that distinguishes the two circulations. In

fact, the blood not only takes an opposite course at the place where

they finish and at that where they begin; but its nature changes also

entirely, and in this respect the two capillary systems, pulmonary

and general, present to us the most important phenomena of the living

economy, viz. the first, the transformation of black blood into red,

the second, that of red blood into black.

There are evidently three things to be examined with regard to each of

the circulations, 1st. the origin; 2d. the course; 3d. the termination

of each kind of blood. In the origin and termination, there is on

one hand the mechanical phenomena of circulation, on the other the

phenomena of the transformation of the blood. In the course of this

fluid there is only the mechanical phenomena of the circulation to be

observed.

_General mechanical phenomena of the two circulations._

By examining these phenomena in a general manner, we see, 1st. that the

red blood going from the lungs, is formed into larger and less numerous

columns, as it approaches the cavities of the heart; that it is in the

greatest masses in these cavities, and that from them to the capillary

system, it is continually dividing into smaller columns; 2d. that the

black blood going from the general capillary system, is formed into

columns larger and less frequent, as it approaches the right cavities

of the heart; that these cavities contain the greatest quantity of

it, and that from them to the lungs, it is successively divided into

smaller columns.

The two kinds of blood circulate then on the two sides in branches that

diminish as they go from the heart, and increase as they approach it.

Represent to yourself for each of the two circulations two trees united

at their trunks, sending their branches, one of them to the lungs, the

other to all the parts. Each of the two parts of the heart is between

these trunks, which it serves to unite, so as to form a general canal

of which we have spoken.

Authors have commonly considered the arteries and veins as forming,

each by their assemblage, a cone, the base of which is at all the

parts, and the apex at the heart. This manner of describing them arises

from this, that the sum of the branches is greater in diameter, than

that of the trunks from which they arise; now in adopting this idea,

it is evident that each half of the heart is at the summit of two

cones, which would be united without it. The pulmonary veins represent

one, and the aorta the other for the red blood; for the black blood,

there is on one part the venæ cavæ and coronary veins, on the other,

the pulmonary artery, which form the two cones. In each circulation,

one of these cones is remarkable for its small size; it is that of the

lungs; the other for its great extent; it is that of all the parts.

Placed between these two cones, each part of the heart should be

considered as an agent of impulse which hastens the course of the

blood, on one hand towards all the parts, on the other towards the

lungs. In fact, if in each circulation these two cones communicate by

their apex, it is evident that the parietes of the vessels that compose

them would be insufficient to maintain the motion, from the base of one

to the base of the other; that is to say from the general capillary

system to that of the lungs, and reciprocally from that of the lungs

to the general one. The course is manifestly too long, and the vital

forces of the vascular parietes not sufficient to admit of this; hence

the necessity of the heart.

This consequence leads to another, which is this. As the red blood has

a greater extent to go over from the heart to the general capillary

system, than the black blood has from the heart to the pulmonary

capillary system, it is necessary that the portion of this organ

belonging to the first kind of blood, should be endowed with a greater

force than that destined to support the motion of the latter. Nature

has effected this object by composing the ventricle with red blood

of fibres much stronger than those of that of black blood. As to

the auricles, as they only receive the blood and transmit it to the

ventricles, their thickness is nearly uniform.

From this we see, 1st. that the part the heart performs in the two

circulations, is absolutely relative to the mechanical phenomena of

the course of the blood, and that, if it has any influence upon the

composition, it can only be by the internal motion it communicates to

it; 2d. that if the course of the two circulations, of black blood and

red, was of less extent, they might do without this intermediate agent

of impulse. This is precisely what happens in the system of abdominal

black blood, the two trees of which distributing their branches, one to

the gastric viscera, the other to the liver, unite by their trunk in

what is called the sinus of the vena porta, which occupies exactly the

place of the heart in the great system of black blood and in that of

red.

It is then possible to conceive, 1st. how the heart may fail; of this

we have many examples, in which the two great circulating systems

resemble in a certain degree, the abdominal; 2d. how the blood can

oscillate from one capillary system to the other, during a considerable

time, though the heart, weak, enfeebled, and even in part disorganized,

can hardly any longer accelerate the course of this fluid; 3d. how,

this organ having entirely suspended its pulsation in syncope,

asphyxia, &c. there is still an oscillation, a real progression of the

blood from one capillary system to the other, so that if an artery or

vein is then opened, it flows a little at the opening. Certainly this

oscillation is very weak; it cannot last a long time; but we cannot

deny that it exists without the influence of the heart, since the black

blood is carried without the agent of impulse, from the intestines to

the liver; hence it follows that the cessation of the pulsation of

the heart is not a proof of the want of motion in the blood, as some

authors have thought. 4th. We know that in many animals of the lower

classes, there is no heart, though there are distinct vessels and

circulating fluids.

The importance of the part that the heart enjoys in the animal economy

is only in relation to the general impulse that it communicates to

all the organs and the constant excitement in which it keeps them by

this impulse. It does not send to them the materials of secretion, of

exhalation and of nutrition; it only in this respect transmits what it

receives from the lungs.

II. _Reflections upon the general uses of the circulation._

This leads us to some reflections upon the general differences of the

uses of the two circulations; differences which prove the necessity

of presenting the single function that results from them in the view

in which I have placed it, and not in that in use in the treatises on

physiology. The following are the differences.

_General uses of the circulation of the red blood._

It is the circulation of the red blood that alone furnishes the matter

of secretions, except that of the bile, a fluid which however deserves

a further examination. It is from this circulation that the serous,

cellular, cutaneous, medullary exhalants, &c. draw the fluids that

they transmit upon their respective surfaces. All the vessels that

carry the matter of nutrition of the organs are also continuous with

the arteries and consequently their fluids come from the red blood.

In the organs even in which the black blood goes, as in the lungs and

the liver, there are vessels with red blood evidently for the purposes

of nutrition. It is the red blood that communicates to the organs of

the whole body that general agitation which is necessary to their

functions, an agitation so evident in the brain. The circulation of red

blood is then the most important; it is that, whence are derived the

great phenomena of the economy.

_General uses of the circulation of black blood._

The circulation of the black blood, on the contrary, having no

connexion with any of the functions, seems only destined to repair, if

we may so say, the losses the blood has sustained in the preceding

one. Observe in fact that a considerable part of the red blood is

expended in the exhalations, secretions and nutrition. The principles

it borrowed in the lungs and which gave it a vermilion colour, have

been left in the general capillary system. It is necessary that the

black blood should receive what the other has lost; now a variety of

substances enters the great canal that contains it. These substances

are internal or external. 1st. The great trunks of the absorbents

constantly pour in the lymph of the cellular texture and of the

serous surfaces, the residue of the nutrition of all the organs, the

super-abundant fat, synovia and marrow. All that which is to be thrown

from within out, is first poured into the black blood. 2d. All that

which enters in from without, is also received by it. The chyle, the

product of digestion, is at first uniformly carried into the general

canal, in which it circulates. In the second place, it is with it that

are mixed the substances of the air, which pass through the lungs in

the act of respiration. In fine, when cutaneous or mucous absorptions

take place, the black blood is always the first that receives the

product of them.

It follows from this, that the circulation of black blood is, if we may

so say, a general reservoir in which is poured in the first place all

that is to go out of the body, and all that is to enter it.

In this last respect, it performs an essential part in diseases;

in fact it is undeniable, 1st. that deleterious substances maybe

introduced with the chyle into the economy, and produce ravages there

more or less evident in circulating with our fluids. For this, it is

sufficient that the organic sensibility of the chylous vessels should

be changed; then they admit what before they rejected, as the glands

by changes in their organic sensibility, often secrete fluids that are

usually foreign to them. 2d. We shall prove in the article upon the

cutaneous system, that it is oftentimes the seat of the absorption of

deleterious substances. 3d. We cannot doubt that besides the principles

that colour the blood, there often passes through the lungs deleterious

miasmata which produce diseases, as my experiments upon asphyxia have

proved. The intestines, the lungs and the skin are then a triple gate

open, in many cases, to different morbific causes; now these causes

that enter thus into the economy are all received in the first place in

the black blood; it is not until afterwards that they pass into the red

blood.

An evident proof of this assertion is this, that we produce

phenomena exactly analogous to those which result from them, by

pouring artificially into the black blood those substances that are

introduced in a natural way. Thus when a purgative or emetic infusion

is introduced into the veins, alvine evacuations or vomiting ensue,

precisely as when the substances of these infusions are introduced by

friction upon the skin. The experiments of many physiologists leave no

doubt upon this point. I am convinced that it is possible to give to

animals artificial diseases, by making different substances infused

into their veins circulate with the blood. I shall speak of these

attempts in the article upon the glandular system. It is sufficient for

me to mention them here, in order to prove that the black blood is a

general reservoir in which many substances can enter, either naturally,

or accidentally, and afterwards disturb the functions by passing into

the whole circulating mass. The humoral pathology has undoubtedly been

exaggerated, but it has still real foundations, and in many cases we

cannot deny, but that every thing arises from the disorders of the

humours.

Let us conclude from all that has hitherto been said, 1st. that the

essential part which the circulation of the black blood performs in

the economy, is to introduce into this blood different new substances;

2d. that that of the system of red blood is to expend on the contrary,

the principles that constitute it. One is constantly increasing, the

other diminishing; to give is the attribute of one, to receive is that

of the other. This sketch, which is perfectly true, and founded upon

the most simple observation, appears to me very proper to establish an

evident demarcation between the two divisions that I have adopted for

the general circulation.

Health supposes a perfect equilibrium between the losses the red blood

experiences, and the acquisitions the black blood makes. Whenever this

equilibrium is destroyed, there is disease. If the black blood receives

more than the red blood expends, plethora follows. That which is called

the poverty of the humours, is manifest when more substances go from

the red blood than enter the black.

These are I think sufficient characteristic attributes of the two

great divisions of the general circulation, to justify the point of

view different from other authors, in which I present this important

function of the animal economy.

ARTICLE SECOND.

SITUATION, FORMS, AND GENERAL ARRANGEMENT OF THE VASCULAR SYSTEM OF RED

BLOOD.

From the general idea that we have given of the two vascular systems,

we should form the following of the position in the economy of that

with red blood.

1st. The capillary system of the lungs gives rise to many minute

ramifications, which soon unite into small branches, then into larger

ones, and finally into four great trunks, two for each lung. These

trunks open into the left auricle towards its superior part. 2d. This,

distinguished from the right by having fewer fleshy columns, by its

smaller size, by the greater elongation of its appendix, which is

narrower than that of the other, &c. communicates by an oval opening

furnished with valves, with the left ventricle, the thickness of whose

parietes, the arrangement of the fleshy columns, &c. distinguish it

from the right. 3d. From this ventricle goes the aorta, the common

trunk whence arise all those that carry red blood to all the parts,

where they terminate in the general capillary system.

The first tree of the system of red blood, the trunk of the second and

the heart that serves to unite them, are found then concentrated in

the cavity of the thorax, whilst the branches of the second trunk are

distributed among all the organs of the economy, and even to all its

extremities.

It is nearly between the superior third of the body and the inferior,

that is found the agent of impulse of the red blood, or the heart.

This position is important; it places under a more immediate influence

of this viscus, the superior parts, the head especially, all of

whose organs, and particularly the brain, require inevitably a very

active and habitual excitement from the blood, in order to keep their

functions in permanent activity. Thus observe, that in the gangrene

of old people, and the affections that arise from the blood not being

driven with sufficient force to all the parts, it is the extremity of

the foot that is first affected, and that of the head and the hands

become much later the seat of mortification. In general, there are

many differences between the phenomena that take place in the superior

parts, and those that happen in the inferior. We shall see in the

dermoid system, that the portion of the general capillary system which

belongs to the first, is penetrated with blood with infinitely more

ease, than the portion belonging to the inferior parts, as asphyxia,

apoplexy, submersion, different cutaneous eruptions, injections

even prove, which in young subjects blacken rather the face than the

inferior parts; now this difference arises evidently from the relation

of position of the superior and inferior parts with the heart.

We have no general remarks to offer here upon the first tree and upon

the agent of impulse of the circulation of red blood. In fact, the

remarks belonging to the lungs and the heart will be given in the

Descriptive Anatomy. It is then especially the second or arterial tree,

whose distribution is now to occupy us. It is necessary in this article

to examine the origin, course and termination of it.

I. _Origin of the Arteries._

This article comprehends the origin of the aorta at the left ventricle,

that of the trunks which arise from it, then that of the branches, the

smaller ones and the minute ramifications that go from them.

_Origin of the Aorta._

Most authors have described inaccurately the manner of the union of

this great arterial trunk with the heart. This is the manner; the

internal membrane of the heart with red blood, after having lined

its ventricle, approaches the opening of the aorta, is attached

there, forms by its folds the three semi-lunar valves, and stretching

afterwards into the artery, covers it in its whole extent. It is this

internal membrane that forms the union of the artery with the heart.

The peculiar or fibrous membrane is not identified with the fibres of

the heart. Its extremity is cut into three semi-circular festoons,

which correspond with the semi-lunar valves that they support. These

festoons do not extend to the fleshy fibres; there is between them and

these fibres a space of two or three lines that the internal membrane

alone covers. Between them and consequently between the valves, we

perceive three little empty triangular spaces, covered by the membrane

also. To distinguish this structure clearly, the origin of the aorta

must be dissected well from without, and stripped entirely of the

fatty texture that surrounds it. Then by cutting this artery and the

ventricle, and by examining when held up to the light the union of one

with the other, after having first removed the valves, we distinguish

very well by the transparency of the internal membrane and the opacity

of the three festoons that commence the aorta, the arrangement that

I have just pointed out. It follows from this, that if the artery is

accurately dissected on its exterior, and we detach from below upwards

the internal membrane that forms the great canal of the circulation of

the red blood, the artery is entirely separated from the heart. This

entire separation of the fibres of the aorta from those of the heart,

would alone be a strong presumption that their nature is not the same

if many other considerations did not prove it in the most evident

manner.

_Origin of the trunks, branches, smaller branches, &c._

Arising thus from the left ventricle, the aorta divides almost

immediately into two branches, one ascending goes to the neck, head

and superior extremities; the other descending to the chest, abdomen

and lower extremities. The first being very soon subdivided into four

principal trunks, differs in this respect from the second, which forms

for a long time one trunk only. The latter having to go over a much

greater distance than the other, preserves with more certainty by this

arrangement the whole of the motion that is given to the blood by the

heart; this does not prevent, however, owing to the less distance, the

impulse from being more sensibly felt by the superior than the inferior

organs, as I have said above. At the superior part of the pelvis, the

aorta divides into two secondary trunks. Soon after, subdivisions begin

under the name of branches, which are afterwards multiplied under that

of ramifications, &c.

Mathematical anatomists have exaggerated the number of the arterial

sub-divisions. Many have thought there were a hundred to one artery;

Haller reduced the number to twenty, and even less. To ascertain

what is really the case, it is necessary to take the arteries at

their origin, and follow their course under a serous membrane, the

peritoneum for example, where they are every where very apparent; it

will be seen in this way, that the sub-divisions are not more numerous

than is stated by Haller; I have frequently satisfied myself of this.

Besides, the inspection of a living animal whose abdomen is opened, is

almost the only means that can be employed without danger of mistake.

Injections when too coarse do not fill all the branches; when too

fine, they pass into the exhalant vessels, and communicate to the

whole serous surface a colour that is not natural to it. It is almost

impossible to ascertain by injections, the precise point of the natural

circulation. To be convinced of this, inject a dog and open the abdomen

of another of the same size; you will see uniformly in one more or

less vessels injected, than are seen in the other filled with blood.

I frequently performed this experiment, at the time I was engaged in

demonstrating the insufficiency of injections, either fine or coarse,

to show the quantity of blood in any part.

When they divide, the arteries form among themselves very different

angles. Sometimes right angles, as at the middle intercostals;

sometimes obtuse, which is more rare, as at the superior intercostals;

most commonly they are acute, particularly in the extremities. The

origin of the spermatic artery is an instance of the extreme of this

last kind of origin.

We observe in general, that wherever there are two divisions, one is

larger than the other. The largest follows the original direction of

the principal trunk, from which the other is more or less separated.

In the interior of the artery, an eminence formed by the fold of the

internal membrane, corresponds with the angle entering from without,

and breaking the column of the blood, favours the change of its course.

This eminence presents an arrangement, that is very variable, which is

owing to the angle of origin. 1st. If the angle is a right one, the

eminence has a circular arrangement and is equally evident in the whole

circumference. 2d. If the angle is acute, as at the mesenteric, then

this eminence is very evident between the branch that arises and the

continuation of the trunk; it forms even a kind of semi-circular spur

or projection, but between the trunk itself and the branch that arises

from it, the union of which forms an obtuse angle, this eminence is

less conspicuous. The more obtuse the angle is, and consequently the

more opposed it is to acute, the less sensible is this second eminence;

it has like the other a semi-circular form, and makes by its union with

it a whole circle which is oblique; so that the portion of the circle

formed by this second eminence is nearer the heart than that made by

the other. 3d. If the angle of origin is obtuse, and consequently that

formed by the branch with the continuation of the trunk is obtuse,

things are then arranged in an inverse manner. There is at the mouth of

the artery an oblique circle, the prominent half of which is nearest

the heart.

The origin of the arterial trunks is generally pretty uniform; but that

of the branches is so variable, that hardly any two subjects have the

same arrangement, in this respect. Take for example the hypogastric;

it would be impossible to form the least idea of its branches, if,

neglecting the manner they separate from each other, you paid attention

only to their course and distribution. These numberless varieties in

the forms, are a remarkable character in organic life to which the

arteries belong. This character must be placed at the side of the

constant irregularity of the arteries. There is no symmetry in their

general distribution, as in the distribution of the nerves of animal

life. Those even of the extremities, that correspond, differ frequently

in their mode of origin and the course of their branches.

The branches, smaller branches, &c. arise at distances very near

each other. There is hardly any, except the carotid, internal iliac,

&c. that runs a considerable course without furnishing some. Thus

experiments in which it is necessary to introduce tubes into arteries,

to open them, &c. can scarcely be made except upon the first of these,

they are prevented in others by divisions that arise from them and

hinder us from raising the artery to any considerable extent.

The origin of the arterial trunks, branches, smaller branches and

ramifications, does not take place in a gradual and necessarily

successive manner. Thus the smaller branches, and the ramifications

even, arise equally from trunks and branches; for example, the

bronchial, thymic arteries, &c. go from the aorta, and yet they are

not so large as most of the divisions of the tibial, which is itself a

third division of the aorta.

II. _Course of the arteries._

In their course the arteries present differences according as we

examine, the trunks, the branches and smaller branches.

_Course of the trunks and branches._

The trunks are the first divisions continuous with the two great

portions of the aorta; such are above, the internal and external

carotids, the subclavians, &c.; below, the iliacs, the hypogastrics,

&c. Generally they are situated in broad interstices, that contain much

cellular texture, as in the groin, the axilla, the neck, the sides of

the pelvis, &c. By dividing they form branches that are received into

smaller and narrower interstices, and are consequently more exposed

to the influence of the neighbouring organs. Both of them are covered

almost every where by a thickness of parts that protects them from

external injury. Besides this protection that the neighbouring parts

and particularly the muscles afford them, they accelerate also the

circulation of the blood, and reciprocally the motion of the arterial

trunks gives to the neighbouring organs and even to the whole limb,

a sensible motion, an agitation that supports its vital energy. This

agitation, which it is often difficult to perceive, sometimes becomes

very evident upon mere inspection. When the elbow is rested upon

the table, and a body of considerable length held in the hand, its

extremity is seen to vaccillate, to rise and fall a little at each

pulsation. If the legs are crost, being first bent upon the thighs,

a spontaneous rising is noticed in that which is supported. To this

we must refer also the cerebral motion, that which is communicated to

tumours that are situated over a great artery, &c. &c.

The trunks and the branches are accompanied by veins, and surrounded

in general with a large quantity of fat, a circumstance that has been

considered favourable to the opinion of those who think that this fluid

is exhaled by the pores of the arteries. We have already said what

should be thought of this opinion.

The direction varies in the trunks and the branches. Usually straight

in the trunks, as in the carotids, the internal and abdominal iliacs,

it renders the circulation less evident. When these trunks are exposed

in a living animal, we do not see any kind of locomotion there, as we

do when the curves are great. There is however some exception to this

rule as it respects the direction of the trunks; the arch of the aorta

is an example of it, so is the internal carotid, which has numerous

curves, which are thought incorrectly, to be necessary to prevent

the impetus of the blood from producing derangement in the delicate

substance of the brain. More tortuous in the branches, this direction

occasions the arterial locomotion that constitutes almost exclusively

the pulse, according to many physicians.

_Course of the smaller branches, ramifications, &c._

Whilst the trunks occupy the large interstices that are left between

several organs, and the branches the smaller ones that separate

particular organs, the smaller branches are found in the interior of

these same organs, without, however, entering into their intimate

structure. Thus in the muscles, they are interposed between their

fibres; in the brain, in the circumvolutions; in the glands, between

the lobes that form them, &c. By them, an internal motion communicated

to the whole organ, facilitates its functions by supporting its partial

activity, as the motion of which I spoke above, supports the general

activity of the part. Besides, the sudden cessation of life, when the

blood ceases to agitate the brain, proves the immediate connexion

between this internal motion and its energy. Thus we observe that life

is much more active wherever the arteries are numerous, as in the

muscles, the skin, the mucous surfaces, &c.; whilst on the contrary its

phenomena are weaker and more obscure in the less vascular organs, as

in the tendons, the cartilages, the bones and the other white parts.

In the smaller branches, the windings are much more evident than in

the branches. Injections make them very conspicuous, especially in the

brain; but as they depend principally upon the cellular texture they

disappear in part, if we separate from it the vessels of all the parts.

Do these windings diminish the rapidity of the circulation, and does

the straightness of the arteries increase this rapidity as much as

physiologists suppose? I think they have exaggerated the effects of the

direction of the arteries; the following are proofs of it. 1st. If in

living animals we expose the hollow organs, as the stomach, intestines,

&c. alternately in a state of fulness and in that of vacuity, I have

observed that the circulation is almost equally rapid in both cases,

though fulness renders almost straight the vessels of these organs, and

that emptiness, by forcing them to wrinkle, increases their curves.

2d. I have opened the carotid artery of a dog, and having observed the

force with which the blood is thrown out, I have also opened both sides

of the thorax; immediately the lungs are collapsed and consequently

the windings of their vessels increased; notwithstanding this no

diminution in the force with which the blood escapes from the artery,

after having gone through the lungs is immediately sensible. It is only

gradually that the force is destroyed by the influence of causes, that

it is not my object to examine. 3d. If in another animal, an artery

being open, we open also the wind pipe, and by a syringe affixed to

the opening suddenly exhaust all the air the lungs contain, this organ

is immediately reduced to a very small size; the vessels become much

bent, and yet I have observed in this case that the blood goes from

the open artery with as much force as before, for a considerable time.

4th. Finally, after having opened the abdomen of a living animal, I

have alternately contracted and stretched the mesentery, whose numerous

arteries had been first opened; no difference is discoverable in the

force with which the blood is thrown out, in either case.

Let us conclude from these experiments, that the influence of the

direction of the arteries upon the course of the blood, is much less

than is commonly thought, and that all the calculations of mathematical

physicians upon the delay of the blood from this cause, rest upon

unsubstantial foundations. There is no doubt that when the fore arm is

strongly bent, the pulse is weakened, stops even, and it is essential

when we feel the pulse that the arm should be extended; but this

phenomenon does not depend upon the angle the artery forms; it arises

from this, that the muscles that press it, contract its caliber and

even obliterate it. This is so true, that the different curves of the

internal carotid are much more evident than the single curve that the

brachial then forms, and yet the circulation is performed there very

well. Besides, open an intercostal artery which has but few curves,

the force with which the blood will be thrown out is not stronger

than it would be from the radial, &c. If the whole arterial system

was empty and the blood going from the heart filled it successively,

as this fluid would strike against the arterial curvatures, it would

undoubtedly experience some delay. It is on this account that in our

injections a tortuous artery is slower in filling; as the spermatic for

example often remains empty. But in a number of tubes full of fluid, it

is wholly different; the impulse received at the beginning of them is

suddenly propagated into all the cavities that form them, and not by a

successive progression, as I shall say hereafter.

The arterial curvatures are adapted to the different states in which

the organs may be found. We see them very evident in those which are

subject to an alternate dilatation and contraction, for example in

the intestines, the lips, and the whole face. In the fœtus, when the

testicle is in the abdomen, the artery is very tortuous. When this

gland descends, the artery untwists and takes the straight course it

has in the adult. In the motions of the womb, the bladder, the pharynx,

the tongue, &c. these curvatures perform an important part in the

preservation of these organs. In the fractures of the lower jaw, they

prevent the rupture of the artery that traverses this bone, a rupture

which the displacing of the bone would produce without them. By them

the arterial system is preserved unhurt in the violent and oftentimes

forced motions that the limbs perform.

The flexibility of the arteries would be insufficient for these

motions; in fact, when an artery is extended longitudinally, its

diameter is diminished. By accommodating themselves to the motions of

our parts, the vessels would impede then the circulation, because there

would be less space for the blood to move in. Hence why the arteries

of all the parts subject to alternate dilatations and contractions,

being uniformly tortuous, can without the aid of their extensibility,

have very different degrees of extent. I would remark upon this subject

that the locomotion of the arteries, observed by Veitbrecht, is far

more evident at the time of the contraction of the hollow organs, or of

the flexion of the limbs, than during the dilatation of the one or the

extension of the others. I have invariably made this remark upon living

animals. We can by emptying or distending the intestines, the stomach,

the bladder, &c. make their arteries beat more or less strong, &c. &c.

_Anastomoses of the arteries in their course._

Anastomosis is the union of many branches, which mingle the columns of

blood that each brings. There are two kinds of anastomoses; sometimes

two equal trunks unite, sometimes a small trunk is joined to a large

one.

The first has three varieties. 1st. Two equal trunks sometimes unite at

an acute angle, and form but one; it is thus that the ductus arteriosus

and aorta are blended together in the fœtus; that the two vertebrals

produce the basilary trunks, &c. &c. 2d. Two trunks communicate at

certain places by a transverse branch; such are the two anterior

cerebral, before they go between the hemispheres. 3d. Two trunks unite

and form an arch; this is the case with the mesenteric; then branches

arise from the convexity of this arch. We see then that there are three

kinds of anastomoses between equal branches; one of these is that in

which two columns of blood are united together and take a direction

between the two first; another in which two columns follow their first

direction, and only communicate with each other; finally in the last,

two columns meet each other by their extremities, in an opposite

direction, and the blood escapes afterwards by secondary vessels.

The second kind of anastomoses is that of considerable branches with

smaller ones; it is extremely frequent, especially in the extremities;

it has no varieties.

It is almost always in regions remote from the heart that anastomoses

are met with. We find scarcely any in the trunks that arise from

the aorta. They begin to be more frequent in the branches, as in

the mesenteric, the cerebral, &c. The more the smaller branches

are subdivided, the more numerous are the anastomoses. In the last

ramifications they are so numerous that they form an inextricable

network. This arrangement is calculated to facilitate the circulation,

which the anastomoses favour in places, where the motion of the blood

is liable to experience obstacles. It is on this account that in the

cavities in which the influence of the neighbouring parts upon the

motion is less sensible, the anastomoses become more frequent, as in

the brain, the abdomen, &c.; whilst they are more rare in the muscular

interstices of the extremities, &c. It is not then a tree with distinct

branches that forms the arterial system, but a tree all the parts of

which communicate together, more frequently as they are the further

removed from the origin.

The principal object of the anastomoses, that of obviating the

obstacles the blood experiences in its course, is fulfilled in many

cases. Thus, after the ligature of a wounded artery or one with an

aneurism, after the spontaneous obliteration of one of these vessels,

we see the anastomoses between the fine branches, above and below

this obliteration or this ligature, continue the circulation in the

part. These collateral vessels then increase often in size; but more

frequently still, the course of the blood is supported almost entirely

by the capillary vessels.

Anastomoses suppose then the vitality of the arteries. It is because

these vessels are not inert, but act themselves upon the fluid they

contain, that the circulating phenomena are subject to so many

variations; that oftentimes, and especially by the influence of

the passions, the spasm of their extremities, principally of the

capillaries, obliges the blood to flow back, a reflux which is favoured

by the anastomoses. This reflux is necessary also in inflammations, in

the different engorgements of our organs, &c. How would the circulation

be able to go on, if all the small branches went to their respective

destinations, without communicating among themselves? Would not the

least embarrassment occasion a troublesome stagnation there?

I would remark upon this subject that the anastomoses furnish the

first proof of a truth which we shall soon demonstrate more in detail,

viz. that in the great trunks, the blood is especially influenced

by the heart, and that in the capillaries, it is exclusively by the

vascular parietes. In fact it is because the vitality of the arteries

is every thing for the motion of the last subdivisions, that the

least alterations that they experience give rise to many engorgements

that inevitably require anastomoses, which are extremely numerous at

the end of the arterial tree. On the other hand, the vitality of the

trunks having scarcely any influence upon the blood, it experiences

but few obstacles in passing through them; there is less need then of

anastomoses, which are in fact more rare there.

If the least cause, the least irritation produced spasm of the trunks,

as they produce that of their last divisions, it would be necessary

that they should communicate as frequently together. A fleshy texture

in the great arteries, and vital properties analogous to the

involuntary muscles, would have required inevitably these numerous

anastomoses, because a variety of causes influencing these kinds of

muscles, they can at any moment increase unnaturally their contraction,

diminish their caliber and embarrass the progress of the fluids that

traverse them.

_Forms of the Arteries in their course._

Many physicians of the present age have described each artery as

forming a cone, the base of which is towards the heart, and the apex

towards the extremities. If we examine a portion of it between the

origin of two branches, whether after having injected it, or by cutting

it perpendicularly when it is empty, or by measuring it when it is full

of blood, we find it always cylindrical. Undoubtedly considered in its

whole extent, it takes a conical form, the effect of its successive

diminution by the branches it furnishes; but in this sense it is less a

cone, than a series of cylinders successively joined to each other and

always decreasing.

Considered in its general arrangement, the arterial system represents

on the contrary, as I have said, a cone absolutely inverted, that is

to say, having its base at all the parts and its apex at the heart;

so that the aorta has a diameter less considerable in proportion,

than that of the sum of all the branches. We have a proof of this by

comparing a trunk with two branches that succeed it; these surpass

it in diameter, and the relation being always the same in all the

subdivisions, we conceive that the capacity of the arterial system goes

uniformly increasing.

This relation of the trunks and the branches has been exaggerated

however by mathematical physiologists, who attributed to the last over

the first a predominance much greater than really existed. A cause of

error upon this point may arise from measuring the arteries at their

exterior after having injected them; in fact, the caliber of the

trunks is greater, in proportion to their parietes, than that of the

branches separately examined; that is to say, other things being equal,

the aorta has parietes thinner in proportion to its cavity, than the

cubital artery; hence, without doubt, why aneurisms are rare in the

branches, and frequent in the trunks, especially when the diseases

arise from a local cause; for if they are the effect of a general

disease, oftentimes the little arteries, the radial particularly, are

also affected; I have already seen two examples of it. This observation

upon the proportions of the arterial parietes proves the impossibility

of judging of the relations of diameter between the two, at least by

examining them in the interior.

Besides, these relations are necessarily very variable, according as

the vital forces which vary themselves so much, increase or contract

the caliber of the small arteries; and in this point of view, this

examination cannot have the importance that was attached to it by the

ancients, whose works are filled with calculations upon this point.

III. _Termination of the Arteries._

After being divided, subdivided, and having the peculiarities we have

just examined, the arteries terminate in the general capillary system.

To point out where this system begins, and where the arteries end,

would be very difficult. We can prove that there the blood ceases to

be entirely under the influence of the heart, and circulates by the

influence of the insensible organic contractility of the vascular

parietes; but how can this line of demarcation be rendered evident to

the eye?

Authors in treating of the termination of the arteries, have considered

their continuity with the excretories, the exhalants, the veins, &c.;

but it is evident that the general capillary system is between the

arteries and these vessels. Thus I shall treat of their origin in

speaking of this system, which is spread in all the organs, but has

essential differences according to the different systems, under the

relation of its continuity with the arteries. In fact, 1st. there are

systems in which these vessels are distributed in great quantity,

and in which consequently the general capillary system contains much

blood; such are the glandular, the mucous, the cutaneous, the animal

and organic muscular, &c. 2d. Other systems receive but few arteries,

as the osseous, the fibrous, the serous, &c. and consequently have but

little blood in circulation in that portion of the general capillary

system that belongs to them. 3d. Finally the pilous, epidermoid,

cartilaginous systems, &c. destitute of arteries, contain only white

fluids in the division of the general capillary system that has its

seat in them.

ARTICLE THIRD.

ORGANIZATION OF THE VASCULAR SYSTEM WITH RED BLOOD.

I. _Textures peculiar to this organization._

The red blood circulates, as I have said, in a membrane arranged in

the shape of a great canal, variable in its form, extended from the

pulmonary capillary system to the general one, and having every where

the greatest analogy. At the exterior of this membrane, nature has

added a fibrous coat for the arteries, fleshy fibres for the heart, and

a peculiar membrane for the pulmonary veins. I shall speak here only

of the arterial coat. The fibres of the heart and the membrane of the

pulmonary veins will be examined, one in the organic muscular system,

the other in the system with black blood. As to the internal membrane

of the arteries, which is also that of the whole system with red

blood, we shall examine it in a general manner.

_Peculiar Membrane of the Arteries._

This membrane is firm, compact, very apparent in the great arteries,

less evident in the last divisions where it is insensibly lost. Its

colour is usually every where the same. If the branches appear red

in living animals, and the trunks yellowish, it arises only from the

transparency of the one which allows the blood to be seen, and the

opacity of the others. The colour of the arterial fibre is yellowish.

However it assumes in certain cases a greyish appearance. I have often

observed in arteries exposed to maceration, that it reddens in a very

evident manner at the end of some days, or rather that it takes a rosy

tinge, very analogous to that of the cartilages of the fœtus and of

the fibro-cartilages of the adult, submitted to the same experiment.

This result is however less uniform in the arteries than in those two

systems, in which it is never absent. Sometimes the internal membrane

reddens also, but never the external or cellular; on the contrary, the

longer this remains in water the whiter it becomes. When the fibrous

coat of the arteries has continued some time with this redness, it

gradually loses it, if maceration is continued. This phenomenon is

often more evident in the branches than in the trunks. For example,

the arteries at the base of the cranium become red very frequently

in the dead body, by remaining in the fluids with which this part is

moistened. We see, in opening the cranium, this redness which does not

belong to the blood left in the arterial cavities, as we may be easily

convinced.

The thickness of the peculiar membrane of the arteries is very evident

in the great trunks. It constantly diminishes; a circumstance that

distinguishes it essentially from the internal membrane, which I have

found almost as thick in the tibial artery as in the aorta. It has

been thought that in certain arteries, as in the cerebral, the fibrous

coat is entirely wanting. There is no doubt that in the vertebral and

internal carotid it is thinner in proportion than in equal trunks

situated in the muscular interstices; but by examining attentively

these arteries, I have clearly distinguished circular fibres in them.

Has the thinness of their parietes an influence upon the sanguineous

effusions, which are, as we know, so frequent in the brain? I cannot

say. These effusions take place only in the capillaries, the trunks

are never the seats of them; now it is impossible to examine these

capillaries. I have sought in vain to ascertain by injections the

vessels torn in apoplexy. Besides, this hemorrhage does not resemble

that of the serous membranes; it is not an oozing through the exhalants

of the ventricles; for these cavities are very rarely the only seat

of it. Almost always these effusions take place even in the cerebral

substance, generally nearer the posterior than the anterior lobe. The

cerebellum is rarely affected by it. When the tuber annulare becomes

so, there are often small partial effusions there, separated by

medullary partitions that remain uninjured.

As to the arteries of the other parts of the body, their peculiar

membrane presents generally a pretty uniform arrangement. It has

appeared to me however, that in the interior of the viscera, of the

liver, of the spleen, it is rather thinner than in the intermuscular

spaces, and even than in the muscles.

This membrane is composed of very distinct fibres, adhering to each

other, easily separated however, arranged in layers, in such a manner

that after having raised the cellular covering, we can without

difficulty separate these different layers from each other; it is

this that has made many authors believe that the great arteries were

composed of a great number of coats. The fibres that form these layers

are circular or nearly so; the external ones appear to be attached to

the compact cellular texture that is contiguous. In fact, by raising

this, a number more or less considerable adheres to it always in an

intimate manner. As to the internal membrane, it does not appear to

furnish any attachment; we raise it easily, without bringing with it

any arterial fibres. The manner of the adhesion of these fibres with

the compact neighbouring texture, appears to me to have great analogy

with the origin of the organic muscular fibres, which are attached in a

great number of places, to the sub-mucous texture.

When a branch arises from a trunk, the circular fibres of the last

separate and form on each side a half ring, whence arises a complete

one, which embraces the small rings formed by the circular fibres of

the arising branch. These circular fibres go even to the eminence of

the common membrane, which is seen within the arterial cavity and

of which I have spoken; so that the whole thickness of the peculiar

membrane serves as a support to their origin. But there is but little

continuity between the two kinds of fibres. Those of the branch do not

arise from those of the trunk; it is the internal membrane that serves

to fix them together, as fibres of communication. Dissection shows

easily these branches set at their origin in the ring which arises from

the separation of the circular fibres. We remark this at the origin

of the intercostals and lumbars upon the aorta, &c. When two trunks

of an equal size go off, as the iliacs, the last circular fibres of

the primitive trunk which they formed, interlace intimately with the

origin of each of the two circular layers, that arise at the fork that

separates this origin. Thus the last rings of the aorta cannot be

separated from the first of each iliac.

There are no longitudinal fibres in the arteries.

What is the nature of the arterial fibre? Almost all anatomists have

considered it the same with the muscular. But if we examine them

attentively, it is easy to be convinced of their differences. The

want of red colour does not establish these differences, since in man

even, some parts really muscular, as the intestines, want this colour.

But the muscular texture is soft, loose and very extensible; the

arterial texture on the contrary is firm and solid, breaks before it

yields. We can observe this, by tying an artery tight. The two internal

coats are cut; the cellular alone is not, though the ligature is

immediately applied to it; we observe, by opening the artery, a section

corresponding with the thread, exactly similar to what a cutting

instrument would have made.

I have often repeated this experiment, pointed out by Desault, upon

the dead body, and upon living animals; the result which is very

uniform, explains the frequency of hemorrhages after the operation for

aneurism. There is undoubtedly no texture so brittle, if I may use the

word, as the arterial, none consequently less proper to be embraced by

ligatures. Why is it that this should be the only one in which it is

necessary to apply them? This phenomenon alone would distinguish the

arterial texture from the muscular. In fact, the preceding experiment,

made upon a portion of intestine in which the fibres are arranged like

the arterial, would produce a flattening, an approximation of these

fibres, but would not cut them.

Moreover compare the properties of texture of the arteries with

those of the muscles; compare their vital properties, by examining

the articles in which I treat of these properties; compare their

development, and especially the different morbid alterations to which

the two are subject, and you will see that there is not a single

relation in which they have the least analogy. The aneurism of the

heart and that of the arteries have nothing in common but the name.

In one there is a rupture of the arterial fibres, a dilatation of the

cellular coat; in the other an unnatural increase, a real development

of muscular fibres which preserve their appearance and their

properties.

Notwithstanding the ease with which the arterial fibres are broken in

cases of aneurism, they enjoy in a natural state a very considerable

degree of resistance and force; another character that distinguishes

them from the fleshy texture. The following are the proofs of this

resistance, which takes place both transversely and longitudinally.

1st. If we tie the carotid artery above, and drive a fluid afterwards

into it, great force must be employed to break its texture. The same

thing happens when we force in air instead of a liquid. Frequently

the efforts of a man are insufficient to produce a rupture; thus the

force of the heart can never cause it suddenly; so that the formation

of aneurisms takes place only from the long continued action upon the

arterial parietes; I doubt whether these tumours can be formed, without

a previous alteration of the arterial texture, by the force of the

impulse of the blood alone against the weak parietes of the arteries.

2d. The resistance of these parietes takes place longitudinally also.

If we draw in a contrary direction, the two ends of an artery and of a

muscle, we effect with more difficulty the rupture of the first, when

the dead body is the subject of this comparative experiment. But upon

the living the effect is opposite; the vessel yields to a very strong

action made upon it; it would be necessary that this action should

be incomparably greater to divide the muscle. This difference arises

evidently from the vital properties of the latter, which in this case

contracts violently, whilst the artery can make no further resistance

than from the nature of its texture. Besides, this longitudinal

resistance to distension is less than the lateral resistance opposed to

the injection; experiments prove it, and it arises without doubt from

this, that no fibre, in the first case, is found directly opposed to

the effort.

This resistance of the arterial texture, so different from that of

the venous, is a necessary consequence of the situation of the heart

at the origin of the arteries. In fact, this organ driving the blood

with force into their tubes, should find there a force capable of

resisting the greatest efforts of which it is susceptible, when its

sensible organic contractility is raised to a high point. This is the

great advantage of the arterial texture. What would become of the

circulation and all the functions that depended upon it, if the least

cause which increased the force of the blood could dilate the parietes

of the arteries beyond the ordinary degree? It was necessary that their

texture should render these parietes independent of the different

degrees of motion of the fluid that circulates in them; whence it

follows that a fleshy heart and resisting arteries are two things

inevitably connected. If nature had doubled the energy of the heart,

she would have doubled also the arterial resistance. On the other hand,

they would have had but little resistance, if there had not been an

agent of impulse at their origin; this is precisely what happens in

the hepatic portion of the vena porta, which by its distribution is

analogous to the arteries. Why is the pulmonary artery thinner and

less resisting than the aorta? Because the right ventricle being less

fleshy, is not capable of so great efforts.

From what has been said, it appears, that the external arterial

membrane resembles the fibrous organs, which, as we shall see, are

characterized by an extreme resistance. But if we observe on the other

hand that this membrane can be broken, raised by layers and scales in

dissection, that it is elastic and even dry, if I may so say, whilst

the fibrous organs are compact, form a solid body, resisting, but

softer and more elastic, we shall be convinced that this external

membrane is exclusively peculiar to the arteries; that it has no

relation with the other systems, but forms a distinct and separate

texture in the economy. The structure with regular fibres, is the only

circumstance that can, in my opinion, make us believe in the muscular

nature of the arteries; but the ligaments and tendons are fibrous

also; of what importance are the forms to the intimate nature? Now,

can we say that this nature is the same, when the physical properties,

when the extensibility and contractility of texture, when the vital

sensibility and contractility are different?

Besides, the action of different re-agents upon the arterial texture,

proves clearly how much it differs from the muscular. There are then

general phenomena common to all the solids; but different peculiar

phenomena that are distinctive. We may satisfy ourselves of this, by

comparing the following article with that which corresponds with it in

the muscular system.

_Action of different agents upon the arterial texture._

The action of the air by drying the arteries gives them a colour of

a reddish yellow, very deep and even blackish in the great trunks,

more clear in the smaller ones. Thus dried, the arterial texture

is almost as hard as the cartilages in the same state, extremely

brittle, breaking in the great trunks with a crackling noise, that is

not perceived in any other animal texture. It is especially in this

preparation, that we see how much the cellular covering of the arteries

differs from their peculiar texture. This covering remains pliable;

it is whitish when raised up separately. Immersed again in water, the

arteries assume in part their natural arrangement.

In drying, the arterial texture loses but very little of its thickness;

this is a phenomenon that distinguishes it from most of the other

textures. It arises from the small quantity of fluid that is contained

between its layers, a circumstance that appears to be owing to the

absence of the cellular texture. In opening the arterial layers, the

kind of dryness they exhibit is remarkable, when compared with the

moisture in which the muscular fibres are immersed.

Exposed wet among other organs to the action of the air, the arteries

putrefy with great difficulty. Their texture resembles in this respect

that of the cartilages, the fibro-cartilages, &c.; it is like them for

some time almost incorruptible; when it is left to putrefy by itself,

it gives out an odour much less fœtid than that of other textures;

there appears to be less ammonia disengaged from it. The absence of

fœtor is also very remarkable in the water in which the arteries have

been macerated, entirely separated from every neighbouring texture. By

comparing this water with that in which muscles have been macerated,

the difference is striking. An evident proof of the resistance of the

arteries to putrefaction and maceration, is what is observed in the

viscera, which have been a long time macerated or which are putrid,

as in the liver, the spleen, the kidnies, &c. In both cases, in the

first especially, these viscera are reduced to a kind of pulp; the

arteries however have preserved their texture still hard, amid this

general softening. By removing carefully the putrid substance, we can

follow them even to their final ramifications. This method of seeing

the arteries is easy, whether they are filled by injection, or left

empty. In the living animal, these vessels are also infinitely less

susceptible of putrefaction than the skin, the cellular texture, &c.

An artery often passes through a mortified part without undergoing any

alteration from it; this is frequently seen in gun-shot wounds.

At the end of a period, very different according to the degree of

temperature, the arterial texture yields finally to maceration

and putrefaction. In the first case, it softens gradually without

changing colour, loses the adhesion of its fibres, and is ultimately

resolved into a pulp almost homogeneous and greyish. In the second

case, it becomes greyish at first, then is reduced also to a pulp,

and when all the fluid part is evaporated, there is left a kind of

coal wholly different from that which remains after the putrefaction

of the muscles. In general, it requires much longer time to soften

the arterial texture by maceration than by putrefaction; which shows

the superiority of the action of the air over that of water, in the

production of this phenomenon.

Exposed to the contact of caloric, the arterial texture curls up,

contracts and exhibits the horny hardening in the highest degree.

If the action of water is added to that of caloric, which produces

boiling, the following is the result of it. 1st. Very little froth

rises before ebullition, from the vessel that contains the arterial

texture; we might say that this texture and the muscular present in

this respect, two opposite phenomena in the economy; the small quantity

of froth that arises from the first, is greyish. 2d. At the moment

of ebullition, there is an evident horny hardening, less however

than that of the nervous texture, more sensible in the direction of

the diameters than in that of the axis; a hardening accompanying

this horny hardening, and a yellowish tinge of the liquor. 3d. This

state continues for half an hour or more, ebullition constantly going

on. 4th. Successive softening; but at the same time a greyish tinge

succeeding to the yellow colour; want of adhesion among the fibres,

increasing as the ebullition goes on, so that they break with great

ease. 5th. However prolonged may be the ebullition, the arterial

texture is never reduced, like the fibrous, the cartilaginous, &c. to

a gelatinous and yellowish pulp. The fibres remain as they are, in the

same relation, with the same size, &c. The want of adhesion and the

change of colour are almost the only phenomena they experience. 5th.

The broth, produced by the boiling, is insipid and tasteless, a proof

how few neutral salts the arterial texture contains.

The action of the concentrated acids curls this texture, afterwards

softens it, finally dissolves it in the form of a pulp, yellowish by

the nitric, and blackish by the sulphuric.

Most of the others have a less sensible action than these two. When

they are diluted, there is no horny hardening at the moment the artery

is immersed in them; but its texture is gradually softened, and can be

broken with the least effort, as after boiling. It is never reduced to

a fluid state, how long soever it may continue in the acid.

The alkalies, even the caustic, have but little action upon the

arterial texture; immersed a long time in them, this texture remains

almost untouched, loses but little by solution, cannot be broken as it

can after being in the diluted acids, &c.

_Membrane common to the system with Red Blood._

I call that the common membrane which lines the arteries, the left side

of the heart and the pulmonary veins. It can be dissected with ease

upon these two last organs. To separate it from the arteries, it is

necessary to cut through by a very superficial circular section, the

external fibrous layer, raise this layer by laminæ from below upwards;

we come then to the internal membrane, which adheres but little to the

preceding, and can be detached from it in the form of a canal, of very

great extent. It is distinct from it, 1st. by its extreme tenuity, and

the transparency that results from it; 2d. by its white colour; for

it appears yellow only by being applied to the preceding; 3d. by the

entire want of fibres. It is smooth and with a uniform texture like

the serous membranes, which we may be convinced of by holding it up

to the light. Besides, it differs essentially from these membranes by

a kind of brittleness that characterizes it; it is broken and torn by

the least effort. The whole resistance of the arteries resides in their

fibrous coat.

It appears that this membrane, though every where connected, has

however some differences of structure in the different regions. 1st.

It is evidently more delicate in the interior of the ventricle with

red blood, than in the corresponding auricle and in the arteries. 2d.

It yields in the heart and in the pulmonary veins, to dilatations much

greater than those of which it is susceptible in the arteries, in which

it would inevitably break, like the proper membrane, if the blood could

produce as great differences of size in it, as it does in these organs.

3d. When we macerate the heart for some time, this internal membrane

acquires in the auricle and upon the mitral valves, a very remarkable

whiteness, and which is foreign to it in all the rest of its course.

4th. As to the action of the different agents, of the air, of water, of

caloric, &c. it appears to me to be the same every where, and resembles

precisely that upon the peculiar membrane. Only I have thought, that

in the small arteries, the common membrane has the horny hardness more

than this, which on this account wrinkles on the interior in different

places, when a whole branch is immersed in boiling water; this does not

take place in the great trunks.

It is evident from this, that though the common membrane of red blood,

is every where continuous, it is not uniform in its structure; we

shall have occasion to make an analogous observation for the different

portions of the two general mucous surfaces.

The internal surface of this membrane is moistened in the dead body, by

an unctuous fluid, that is found in greater or less quantity. Does this

fluid exist in the living? does it serve to defend the arterial coat

from the impression of the blood? It is difficult to determine. We know

of no organ fitted to furnish it; it would arise from the exhalants,

if its existence, as many authors have admitted, was real. It would

be well to ascertain as to its existence, whether it was merely a

transudation after death, analogous to that of the bile through the

gall bladder, or the consequence of a little serum remaining in the

arteries after the expulsion of the blood. What makes me suspect so

is, that these arteries being deprived of blood, contract intimate

adhesions on their internal surface; which their fluid ought to

prevent, as that of the mucous tubes does, which should they cease to

transmit their respective substances, as the excrements for example,

the secreted fluids, &c. would never be obliterated because of this

fluid.

It appears then that it is the membrane itself, and not a fluid that

escapes from it, which serves to protect the artery; it can, in this

point of view, be considered in relation to the blood, as a kind of

epidermis. It is this, which by its folds contributes especially to

form the aortic and mitral valves, and the different eminences at the

origin of the branches, smaller branches, &c. The external surface,

feebly united to the other membrane as we have seen, has not an

intermediate cellular one. Notwithstanding this slight adhesion, no

means, boiling water, maceration, putrefaction, &c. can detach one of

these membranes from the other, as takes place in the periosteum from

the bone, which, are naturally much stronger united; it requires always

the aid of dissection.

What is the nature of this common membrane? I am entirely ignorant;

though with a different appearance it has the greatest analogy with

the preceding coat, in its properties. We cannot class them in any

system. They form a separate texture in the economy, a texture that has

properties entirely distinct.

When we dry the common membrane of the arteries by itself, it is

infinitely more pliable than the other. It remains transparent, the

other does not. As to the phenomena of the other re-agents, except the

horny hardening, they are nearly the same.

This membrane is remarkable, in all the organic systems, for the

singular tendency it has of being ossified in old age. I have been able

to satisfy myself, that out of ten subjects, there are at least seven

that have incrustations after the sixtieth year. These incrustations,

having no connexion with the peculiar fibrous membrane, begin uniformly

on the external surface of this, the most external part of which they

attack; for there always remains over the incrustation a kind of

pellicle that separates it from the blood, and which belongs to the

membrane; the earthy substance is never immediately in contact with

this fluid.

These incrustations do not follow any of the laws of ordinary

ossification. The cartilaginous state rarely precedes them. The saline

substance is deposited immediately upon the exterior of the common

membrane by the exhalants. It is always in separate plates, more or

less broad, that this exhalation is made; rarely the whole of the

artery forms a solid continuous tube; so that the membranous portions

remaining between the plates can be considered as serving for articular

connexions, and that the arteries, thus ossified, are composed of many

pieces moveable upon each other, and being able to a certain extent to

adapt themselves to the circulating motion.

As long as these plates remain thin, the interior of the artery is as

usual smooth and polished. But if many saline substances are deposited

there, they then have a greater thickness and make a projection within.

The fine pellicle that covers them and which is continued upon the

artery, is broken; then they adhere only by their external surface

to the peculiar membrane. Their circumference is unequal and rough.

If there is a great number in the artery, the whole internal surface

presents numerous asperities, produced by the rupture of this extremely

fine layer of the common membrane that covers the osseous plates. This

arrangement is particularly remarkable at the origin and even in the

course of the aorta. I have noticed it frequently in the dissecting

rooms. Since I have practised medicine in the hospitals, I have already

opened three or four subjects that have exhibited this arrangement, in

which the heart was perfectly untouched, but who died however with most

of the symptoms that accompany diseases of that organ. The rupture of

the fine pellicle when the osseous plates become large, arises from the

remarkable brittleness that we have observed in the common membrane,

of which it is an appendage. I have never seen these osseous plates

entirely detached, and become loose in the artery.

All the parts of the arterial system are subject to ossification. It

appears as frequent in the branches as in the trunks. We know how

common it is to find the radial ossified, in feeling the pulse of an

old person. The ramifications appear to be less frequently the seat of

these incrustations, which never take place in the capillary system; a

circumstance that would induce me to believe that the common membrane

of the arteries does not extend to this system, but that it changes

gradually into a different texture.

It is not only in the arteries that the common membrane of the system

with red blood is penetrated with saline substance; this often happens

to it in the heart, especially in the aortic and mitral valves. It is

more rare upon the internal surface of the left ventricle and auricle

and the pulmonary veins. I have had however examples of these last.

This general disposition to ossification in its whole course, proves

that its nature is every where the same, and that notwithstanding the

differences pointed out, I have had reason to consider it in an uniform

manner, from the pulmonary capillary system to the general; for as I

have already observed, an identity of diseases supposes an identity of

nature. It is the frequency of ossifications of this membrane in the

heart of old people, which renders extremely frequent the intermission

of the pulse at that age. The ossification of the origin of the aorta

has an influence also upon the circulation, as I have ascertained;

but that of the trunks, branches, &c. does not produce the least

derangement.

The ossification of the common membrane of the system with red blood

differs essentially from those that happen in other parts, in this,

that it is, if we may so say, a natural phenomenon, whereas the others

are accidental and often preceded by inflammation and engorgement.

Thus these ossifications do not follow the progress of age; they

happen in young people and in adults, as often as in old ones. Before

old age, the ossifications of this membrane are observed also, but

infinitely more rarely than at this age. The diseases of the heart

which the ossification of the mitral valves accompanies and often alone

constitutes, are a remarkable proof of this. A phenomenon has struck

me many times upon this subject; such an ossification as an old man

can live with very well, and which only makes his pulse intermittent,

produces in the adult the most serious consequences. I have already

opened many subjects, who had been affected with difficulty of

breathing, frequent suffocation, cough, irregularity of the pulse,

necessity of an erect position of the trunk, and in the later periods,

infiltration, serous effusion in the thorax, spitting of blood, &c.

and in whom I have found only ossification of the mitral valves, less

than we see every day in the bodies of old people in our dissecting

rooms. I confess that even this natural disposition to ossification in

the common membrane of the system with red blood, had made me think

that they had exaggerated a little the cases in which this ossification

becomes, in the adult and even in the old man, when it is very strongly

marked, the cause of that series of phenomena, whose assemblage forms

the asthma of most physicians. But the practice of the Hôtel Dieu shows

me every day, that these cases of ossifications, those of aneurisms

and those of other organic affections of which the heart is the seat,

form a class of chronic diseases almost as numerous as that of the

chronic diseases of the lungs, to which generally were referred all the

diseases of the chest, before the time of Corvisart.

II. _Parts common to the organization of the Vascular System with Red

Blood._

_Blood Vessels._

The parietes of the arteries contain secondary arteries destined

to their nutrition. These arteries come usually from neighbouring

branches, sometimes from the artery itself, whose capillary divisions

terminate in the texture of its parietes. The heart exhibits this

arrangement. At its exit, the aorta sends off the coronaries which

are spread upon the texture of this organ and upon the origin of this

artery itself. The bronchials furnish the parietes of the pulmonary

veins. In the arterial texture, in which it is especially necessary to

examine the little arteries, they wind at first in the cellular texture

exterior to the artery, they ramify there in a thousand ways, send some

divisions to the neighbouring organs, but furnish a great number that

penetrate the peculiar membrane, are interposed between its layers,

leave filaments there and terminate before they arrive at the internal

membrane. I have never seen, either by injections, or by opening in a

living animal an artery in which I had first stopt the course of the

blood above and below, as for example, the carotid, I have never seen,

I say, the little arteries penetrating even to this internal membrane.

To distinguish well without injections, the vessels of the arteries, it

is necessary to choose on one hand a great trunk like the aorta, and

on the other to take this trunk in a young animal that has been killed

for the purpose by asphyxia; all the little arteries then are perfectly

injected with a very black blood. Examine the arteries of the fœtus,

especially if it has died by asphyxia at birth, you will be struck with

the great abundance of blood vessels that its great arteries contain

and which are sometimes as livid as in asphyxia.

The veins accompany every where the little arteries in the parietes of

the arterial trunks, they follow nearly the same distribution. I have

not seen them become varicose in the parietes of aneurismatic arteries,

in as evident a manner, as in the tumours of many other textures of the

animal economy.

_Cellular Texture._

The arteries have around them two kinds of cellular texture; one, which

is very external, loose, fatty, full of serum, with distinct layers,

unites them to the neighbouring parts, favours their motions, is in no

way distinct from the rest of the cellular system; the other, firm,

compact, not fatty, filamentous and not lamellated, forms the first of

their coats. We have spoken in treating of the cellular system, of this

particular layer that covers the arteries, which authors commonly call

the cellular coat, which the ancients called nervous, on account of its

whiteness, and which, analogous in every respect to the sub-mucous,

sub-excretory cellular texture, &c. differs essentially from the

preceding, as it differs from that which is in the interior, around or

in the interstices of the organs.

These two kinds of cellular texture, the last especially, contribute to

support the folds of the arteries; as when we have carefully dissected

the peculiar coat, these folds entirely disappear. However when they

are on one hand strongly marked, and on the other, are not subject

frequently to disappear in yielding to the elongation of the parts, as

in the internal carotid in its canal, I have observed that the arterial

fibres are accommodated to these folds; that the fibres are more

numerous on the convex side, than on the other, so that the thickness

of the artery is exactly uniform, which it would not be without this

inequality; for being more pressed on the concave side, these fibres

would make the artery thicker at that place.

The cellular texture forms the first membrane of the arteries, and

gives as we have seen insertions to the arterial fibres, but it does

not extend into the interstices of these fibres; it is this that

distinguishes essentially the layers of the arterial texture, from

those of the muscular, venous textures, &c. I have never been able to

discover the cellular texture there by any means that I could employ.

Maceration, of which Haller has said so much, does not show any thing

like it. When at the end of a very long time, the arteries finally

yield to it, they exhibit only a kind of pulp, in which there is no

cellular appearance.

In general, the resolution of the organs into cellular texture by

maceration, exhibits a phenomenon much less extensive than is generally

thought. It is the organic texture itself that forms the kind of pulp

that is then obtained. As this texture varies in each system, the

pulp of these systems, a long time macerated, varies equally; this

undoubtedly would not happen, if, as Haller has advanced, the cellular

texture was the only base, to which all the organs are brought by

maceration. But let us return to the arteries.

Not only their fibres are not formed of cellular texture; but as I have

said, they do not contain it in their interstices, a character in which

it differs from all the other systems. The most careful dissection

does not show it. When we separate the fibres from each other, we see,

either that they are merely in apposition, or that they are held by

little elongations of the same nature as themselves. I have said that

this absence of the cellular texture is observable between the proper

and common membranes of the arteries, though Haller has pretended the

contrary.

I believe that this absence of cellular texture contributes much to

the kind of brittleness that particularly distinguishes the arterial

texture, and which, as I have observed, renders it the least fit of

all the animal textures, to support ligatures without breaking. It is

to this circumstance also that must be referred the difficulty, the

impossibility even of arterial dilatations, of the formation of cysts

by the parieties of arteries. There are never, we know, true aneurisms;

when these tumours increase at all, the two membranes of the artery

break and the cellular coat alone is dilated. Hence the necessity of

the peculiar structure which distinguishes the cellular texture placed

around the arteries, and gives it a resistance that it has not in most

other parts. Authors are astonished at these ruptures which distinguish

the dilatations of the arteries from those of all the other systems. If

they had compared the texture of the arteries with that of the other

systems they would have seen the reason of this difference.

We easily understand, after what has been said, why there is never fat

in the arterial texture; why it is never infiltrated in dropsies; why

it does not develop hydatids and cysts in its layers, why the different

tumours, for which the cellular texture serves as a base, as we have

seen, do not appear in the arteries, &c. When an artery has been

wounded, either longitudinally or transversely, we do not see fleshy

granulations arise from the edges of the wound; I do not know that

surgeons have seen them in the operations for aneurisms. Never, in the

numerous cases in which I have had occasion to cut the arteries, in

animals, and then leave them free, after having interrupted the course

of the blood, have I observed any thing like it. If an arterial trunk

is laid bare, the cellular coat often furnishes these granulations; but

we never see them, if this coat is removed.

_Exhalants and Absorbents._

Are there exhalants in the arteries? Nutrition undoubtedly supposes

them; but it is not probable, as I have said, that they open upon their

internal surface.

As to the absorbents, I thought for some time, that the absence of

blood in the arteries, after death, arises from this, that their

lymphatics preserving still the absorbent faculty for some time, take

up the serum which is separated from the crassamentum. But lately

experiments have undeceived me. I have enclosed blood, water, the fluid

of dropsies, &c. between two ligatures made above and below on the

common carotid, the body of which had been so managed on the exterior

as not to break the vessels that come to it. At the expiration of a

considerable time I have not discovered any diminution in the fluid.

There had been then no absorption. I would observe that on account of

the want of collateral branches, the carotid is alone proper for these

experiments, and a variety of other analogous ones.

We know that the absorbents abound where there is cellular texture, and

that they are wanting usually where there is none. It is probable then

that the absence of this texture produces also the absence of these

vessels.

_Nerves._

1st. The first tree of the system with red blood, receives almost

exclusively cerebral nerves. We know in fact, that the par vagum is

spread upon all the pulmonary veins, as well as upon the neighbouring

vessels of the lungs, which hardly receive any from the inferior

cervical ganglion. 2d. The middle portion of this system, that in which

the heart is found, derives its nerves almost as much and even more,

from the ganglions, than from the brain. 3d. The great tree with red

blood, or the arterial, is almost exclusively embraced by the first

class of nerves. We have said how these nerves go in this respect.

The cerebral which accompany them, furnish hardly any filaments to

the arteries. There is merely juxta position as we see it in the

extremities, in the intercostal spaces, &c.

I cannot repeat it too much, that the constant relation of the arteries

with the nervous system of the ganglions, deserves the attention of

physiologists, because it is too general not to belong to some great

object of the functions of the economy, though the object may be

unknown.

ARTICLE FOURTH.

PROPERTIES OF THE VASCULAR SYSTEM WITH RED BLOOD.

What we have to say of these properties, will refer particularly to the

arteries, as well as what we have said of the organization. In fact the

fleshy parietes of the heart and the membranous ones of the pulmonary

veins, possess properties that will be examined hereafter, and which

differ from those of the arteries, on account of the difference of

texture. As to those of the common membrane they are nearly the same in

the whole course of the red blood, the organization differing but very

little.

I shall consider the properties of the arteries only in the arterial

texture and in the common membrane; for the cellular coat belonging to

the system of that name, partakes of all its properties.

I. _Physical Properties._

Elasticity, which is obscure in most of the other animal textures that

are characterized by a great degree of softness is very remarkable in

the arteries; it is this that particularly distinguishes them from the

veins. This elasticity keeps their parietes apart, though they may be

empty. These tubes, with the cartilaginous, as the trachea, the meatus

auditorius of the fœtus, &c. which are equally endowed with elasticity,

are the only ones that keep thus open of themselves. All the others

have their parietes applied to each other, when the fluid that runs

through them does not distend these parietes.

It is to the elasticity of the arterial parietes that must be referred

their recovering themselves when they have been flattened so as to

obliterate their cavity, the sudden straightening of an arterial tube

that has been bent, &c.

This property takes also an evident part in that kind of locomotion

the arteries have upon the entrance of the blood. In fact, lay bare a

tortuous arterial trunk in a living animal, you see the whole of it

rise at each pulsation, leave the place it occupied, and straighten

itself, particularly at its curves. At the moment the injection

penetrates a very thin small subject, we perceive also through the

integuments, a locomotion of all the tortuous branches of the face.

Now it is evident that if the arteries were not of a firm and elastic

texture, they would not thus obey the motion that is impressed upon

them; besides, observe what takes place in the injection of the

abdominal branches of the vena porta, which having no valves can be

injected like arteries. Nothing similar to the locomotion of which I

spoke is observed in driving the fluid into them. I have often made

arterial blood circulate in the veins by the means of curved tubes,

fitted to the vessels of a living animal, for example, by making the

carotid and external jugular communicate; now, we observe clearly in

the veins carrying the red blood, a kind of pulsation synchronous with

the beating of the heart, and a distinct rustling noise, but not a real

locomotion.

The locomotion of the arteries supposes three things, 1st, an agent

of impulse, that communicates a motion more or less strong, to the

blood contained in their interior; 2d, a tortuous arrangement which

allows the blood in striking their parietes to straighten them; 3d,

the firmness and elasticity of these parietes which facilitate this

straightening. On the other hand, the parietes must not be too firm;

thus the cartilaginous texture would be improper for this locomotion.

The elasticity of the arteries is as striking after death as during

life; it is essential to distinguish it from contractility of texture.

There are many distinctive characters, the following are the most

striking; 1st. The contractility of texture takes place only when

there is a want of extension of the arterial parietes, that is to say,

when these vessels cease to contain the blood which resists their

contraction, or when they are cut and afterwards left to themselves.

On the contrary, elasticity requires for its exercise, a previous

compression and is manifested by the sudden return of the parts to

their natural state. 2d. Contractility of texture has a permanent

tendency to contraction; we may say that all the parts that possess

it are in a forced state; so that as soon as this state ceases,

contraction takes place. On the contrary, elasticity has not this

constant tendency to exercise. 3d. Every elastic motion is brisk,

sudden, as quick to stop as to begin. On the contrary, every motion

of contractility of texture is insensible, slow, continues often many

hours and even days, as we see it in the retraction of amputated

muscles, &c. 4th. Every organ in which there is contractility of

texture, enjoys necessarily extensibility. On the contrary, this last

property is not necessarily connected with elasticity, as we observe it

in the cartilages of animals, &c. 5th. Elasticity is purely a physical

property. Contractility of texture, without being vital, is only

inherent in the organs of animals.

II. _Properties of texture. Extensibility._

The extensibility of the arteries may be considered, 1st, transversely;

2d, longitudinally.

The arteries have but little extensibility in the direction of their

diameter. 1st. Whatever efforts are made to dilate them by injections

of water, air, fat substances, &c. their caliber is rendered but little

larger than natural. 2d. I have said that their texture is remarkable

by a kind of brittleness, that when the blood distends them a little in

aneurisms, this texture breaks instead of yielding, and that it is only

the cellular coat, which, by the extensibility it has from the system

from which it is derived, that is fitted to form the cyst that contains

the blood. It is this that essentially distinguishes aneurismal from

varicose tumours. 3d. If we tie superiorly the carotid artery of a

dog, the blood pushed against the ligature that stops its course,

reacts violently upon the parietes and yet the dilatation is hardly

perceptible. We must not think however that the arteries do not yield

at all. When the dilating cause acts slowly, it produces its effect

to a certain determinate point, beyond which rupture takes place. The

proof of this, is in the dilatation of the arch of the aorta, in that

which true aneurisms present in their early stages, &c.

Longitudinally, the arteries are more capable of stretching, than

they are transversely. We may be convinced of this, by drawing out

these vessels, to place a ligature upon them in an amputated stump.

By cutting upon a dead body a portion of artery, and drawing it in a

contrary direction, it is evidently elongated. It is necessary in these

experiments, to pay attention to the development of the folds. In fact,

I have said, that this development of the folds performs a principal

part in the elongation of the arteries situated in the parts that are

dilated.

It is evident that in the extensibility in a transverse direction, it

is the circular fibres of the peculiar membrane that especially resist;

that on the contrary, in the extensibility in a longitudinal direction,

it is the common membrane that opposes the resistance, since there are

no longitudinal fibres. It is not astonishing then that the first kind

of extensibility should be less evident than the second.

_Contractility._

It is necessary to consider it in a transverse and in a longitudinal

direction.

Considered in the first point of view, contractility is much more

evident than extensibility. When the artery is no longer distended with

blood, it contracts in a sensible manner. It is to this contraction,

that the following phenomena must be referred; 1st. the umbilical

artery and the ductus arteriosus, become like ligaments after birth,

by the adhesion of their parietes which are contracted. 2d. If we

make a ligature upon an artery, the whole portion comprised between

this ligature and the first collateral branch, soon exhibits the same

phenomenon, as is proved by the operation for aneurism. 3d. If we

include a portion of the carotid between two ligatures, and afterwards

empty it by a puncture, it suddenly loses half its caliber. 4th. In

dogs in whom I have transfused blood in order to produce artificial

plethora, I have observed the arteries to be almost double in diameter,

to what they are in those of the same size, who had suffered great

hemorrhage. Two animals of the same size, one killed by hemorrhage the

other by asphyxia, exhibit the same difference. 5th. These experiments

shew me satisfactorily the cause of a large and small pulse, a cause

admitted moreover by most physiologists. The artery is certainly more

or less large, according to the quantity of blood that fills it. There

is a point of extension that it cannot pass; but it contracts often

for the want of blood, so as to be as it were, but a mere thread. 6th.

Though you may have opened but few bodies, you have no doubt been

astonished, that in those of the same size, the arteries have often

very different diameters. This arises wholly from what takes place at

the moment of death. If, from the want of blood, the arteries are for

a long time contracted, they remain in this state, as happens to the

heart in death by hemorrhage, &c. This is so true, that arteries of

different diameters commonly become equal by injection, which brings

them to an uniform degree of extension that they cannot pass. 7th. In

a longitudinal wound of arteries the ends of their cut fibrous circles

separating from each other, a space, which does not close, is left

between them.

Most authors have confounded contractility of texture of the arteries

with irritability. I have no occasion here to show how much they are

deceived. In none of the preceding cases, is it necessary that a

stimulant should be applied upon the arterial texture; the only thing

necessary is the absence of extension, a distinctive character of the

contractility of texture. Moreover it is evident, that this property

continues after death, though in a less degree than during life;

whereas some hours after death, every kind of irritability disappears.

I think that it is especially in the arterial system, that may be seen

the advantage of my division of the properties of our organs. Read

all the authors upon this system, and you will see that no one is

intelligible, because they have not assigned the limits of the vital

properties and those of texture.