Contractility of texture in the longitudinal direction, is in

proportion less evident than in the transverse; it is however real.

1st. Thus when we cut an artery between two ligatures, the two ends

retract immediately in an opposite direction. 2d. This retraction

is evident in amputation; that of the muscles and the skin however

is greater, the artery often projects a little. 3d. An artery, cut

transversely in a portion of its parietes, often presents at this

place a broad opening, arising from the retraction of the cut parts,

as happens in a longitudinal wound of which I spoke just now. 4th.

When we draw an artery forcibly and suddenly let it go, its retraction

is very evident. In making this experiment upon an animal, the vessel

buries itself in the flesh. Hence why, the spermatic artery and cord,

drawn down by the weight of the testicle, often ascend into the abdomen

after it is removed, if care is not taken to prevent them.

It is this circumstance that has induced me to propose for the

operation of sarcocele, a modification which consists, after having

dissected around the cord after the first incision, 1st, in searching

immediately for the vas deferens, which is easily found by its extreme

hardness; 2d, in giving it to an assistant to hold; 3d, in passing

a bistoury between it and the blood vessels; 4th, in cutting the

blood vessels first and leaving the vas deferens untouched; 5th, in

afterwards tying the artery, which is easily discovered by the jet

of blood; 6th, and then, when this is done in cutting also the vas

deferens. It is evident, that by this section at two different times,

we have the advantage of applying the ligature without fear of the

retraction of the artery, since the vas deferens to which it adheres,

and which is not cut, until it is tied, is sufficient to retain it.

I have not performed the operation; but it is evident that there is

nothing to prevent the execution of this plan, since the parts are

sound where we cut. I have moreover always taught the student to manage

in this way with ease. It is especially when it is necessary to cut the

cord very near the ring, because it is diseased in its course, that

this method of operating appears to me to have great advantages.

I think that the retraction of arteries that have been drawn, and

their contraction afterwards, perform an important part, in producing

the absence of hemorrhage in most wounds by laceration, a singular

phenomenon, that particularly distinguishes these wounds from those

by cutting, even when a considerable vessel happens to be in their

course. Many authors have given examples of this; we find some

particularly in the works of Sabatier.

III. _Vital Properties._

_Properties of Animal Life. Sensibility._

Have the arteries animal sensibility? Upon this point, facts teach

us what follows. 1st. The ligature of an artery sometimes produces

a painful sensation, more frequently it does not. It is especially

in the spermatic that the pain is frequently felt, but this can be

referred to the nerves. 2d. I can without exaggeration say, that I have

made experiments upon more than a hundred dogs, in whom I have forced

various substances through the carotid to the brain, and have irritated

this artery with the scalpel, acids, alkalies, &c. but that the animals

have never given any marks of pain. Many authors have obtained similar

results. 3d. I would observe also, that it is an additional proof of

the kind of insensibility of the nerves of organic life, which as we

have seen are distributed to the arteries. 4th. This is what I have

observed concerning the irritation of the common membrane of the red

blood; the injection of a mild fluid at the temperature of the animal

produces no effect; but an irritating fluid, as ink, a solution of

acid, wine, &c. creates severe pain equal to that arising from the

irritation of the most sensible parts, if we may judge by the cries and

agitation of the animal, the moment the fluid enters the carotid.

_Contractility._

Animal contractility does not exist in the arteries. In fact this

contractility could only depend upon a relation between these vessels

and the brain, by the means of the nerves; now, 1st, any irritation

produced upon this last viscus, occasioning convulsions in the organs

under the influence of the will, has no effect upon the arteries. 2d.

Opium, which in a certain dose, paralyzes, if we may so say, the same

organs, leaves the arterial motion wholly unaffected. 3d. If we lay

the spinal marrow bare, and irritate or compress it, the action of

the arteries is neither increased or diminished, whilst the voluntary

muscles become the seat of convulsions or paralysis. 4th. No effect is

produced upon the arteries by different irritations, whether of the

nerves of the cerebral system, which accompany the vessels without

giving them any apparent filaments, or of the nerves of the system

of ganglions, which are distributed irregularly and in very great

number upon their external surface. 5th. To remove all doubt upon this

subject, I selected galvanism, the most powerful kind of excitement.

Without effect did I arm on the one hand the cerebral nerves, on the

other, the arteries that are joined to them; the contact of the two

armed points does not produce in the arteries the motion it excites

in the muscles in which the nerves are spread. The effect is the same

in experiments upon the nerves of the ganglions. I armed on one hand

the upper part of the mesenteric plexus, on the other, the arteries

of the same name, first stripped of their serous and cellular coat;

the contact was entirely without effect. The arterial system does not

possess that faculty of motion which the action of the brain is capable

of producing. All that has been written by different authors, by Cullen

in particular, upon the nervous power, upon the action of the brain on

the arterial system, is vague, illusory and contradicted by experiment.

_Properties of Organic Life. Sensible Organic Contractility._

The sensible organic contractility is evidently wanting in the system

of which we are treating. In whatever way we irritate an artery in a

living animal, it remains uniformly immoveable. 1st. If we stimulate

the external surface with a scalpel or any other instrument, it is

easy to make this remark. 2d. The same observation is made when we

excite the internal surface, an experiment that I have often made,

because we know that the heart is more irritable internally than

externally. 3d. An artery cut longitudinally in a living animal

does not turn over at its edges like the intestines in similar

circumstances. 4th. An arterial tube, drawn out of the body, never

gives like the intestines, the heart, &c. any mark of contractility.

5th. If we raise the arterial plates, layer by layer, in a living

animal or one recently killed, we see nothing of that trembling, that

palpitation that the fibres of the organic muscles exhibit under like

circumstances; on the contrary, we observe in them a kind of inertia

very analogous to that of tendinous, aponeurotic fibres, &c. 6th. It is

said, that by placing the finger in an artery, a contraction is felt.

I have often made this experiment; the contraction is infinitely less

sensible than has been said; besides it is produced evidently by the

contractility of texture. 7th. Lamure says, that a portion of blood

being intercepted between two ligatures in an artery, the parietes

of it continue to contract, though deprived of the influence of the

heart; this is not correct. It is so important that I have examined it

myself; I have repeated this experiment at least ten times upon the

carotid; the following has always been the result; the tube comprised

between the two ligatures and filled with blood, is agitated by a real

motion, but it is only that of the common locomotion that it partakes

with the whole artery, and which arises from the impetus of the blood

against the ligature nearest the heart. To be convinced of this, it

is only necessary to lay bare a considerable portion of this artery;

we see evidently that the whole tube, whether the portion nearest

the heart, or that comprised between the ligatures, or that which is

beyond, is agitated by a common motion. 8th. Instead of the blood

I have intercepted different irritating fluids in a portion of an

artery; there is the same inertia, the same want of contraction in the

parietes; but the same motion derived from the general locomotion. 9th.

Many authors have produced a contraction on the part of the arteries by

stimulating them with concentrated acids. This is true, and I have also

produced this effect; but it is not the result of contractility, but it

is the horny hardening. Observe also that the arterial texture never

returns to its primitive state after a contraction like this; that the

alkalies, that are as irritating as the acids when the vital forces are

excited, have no effect here; it is the same phenomenon during life, as

that which we have spoken of as taking place after death.

There can be no doubt, I think, after this, that the arteries do not

exercise during life any kind of contraction by themselves and under

the vital influence. All that has been said upon this point, is the

evident effect of the contractility of texture. Thus when we open

an artery between two ligatures, it empties itself of the blood it

contains, or of the fluid that is accidentally pushed there; the same

phenomenon takes place when we place only one ligature that intercepts

the influence of the heart, &c. It is so true, that all these phenomena

and other similar ones depend upon the properties of texture, that

they take place in the dead body as long as an artery is not putrid.

Fill any portion of the arterial system, afterwards open one of its

tubes, it empties itself immediately by contracting. The contraction

produced by the defect of extension, is that which characterizes

the contractility of texture. Irritability or sensible organic

contractility, supposes on the contrary uniformly the application of a

stimulus.

_Insensible Organic Contractility._

Insensible organic contractility or tone very evidently exists in the

arteries. In the great trunks and wherever the pulsation is sensible,

its functions are limited exclusively to nutrition and exhalation,

if this last takes place in the interior of arteries, which I do not

believe. But when the influence of the heart upon the blood contained

in these vessels ceases, which happens at the commencement of the

capillary system, then the tone begins to have an influence not only

upon the nutrition of the vascular parieties, but also upon the

circulation that is going on there; it is even wholly by the tonic

powers, as we shall see, that the circulation of the small vessels is

carried on; the heart has no influence there. I shall treat of this

property under the general capillary system; here it performs but a

very weak part.

As to organic sensibility, it evidently exists in the arteries, since

it cannot be separated from the preceding contractility; like it, it

is obscure in the great trunks, which have only what is necessary for

their nutrition.

From the small development of the organic forces of the arterial

texture, it is evident that this texture would rarely be the seat of

affections, over which these properties particularly preside. This also

is proved by observation.

1st. Acute diseases are rarely observed in the arteries. Among all the

bodies that I have examined, I have found but very few in which there

were traces of inflammation in the arterial texture. I would observe

upon this subject, that it is necessary to distinguish accurately

the redness which is, as we have said, the effect of maceration, and

which even appears spontaneously in the dead body some time after

death, especially in the cerebral arteries; it is necessary, I say,

to distinguish it from that which arises from inflammation. In one

the arterial fibres are really red, in the other they appear so only

by the injection of their vessels. Is the common membrane inflamed in

inflammatory fever? I am entirely ignorant. These simple fevers are

so rare, especially in hospitals that we have hardly an opportunity

of examining patients that have died of them. But by supposing that

this inflammation existed, the infrequency of these fevers considered

in their simple state, would prove even how little the arteries are

disposed to inflame. 2d. The arteries are not often the seat of chronic

affections. Except on the one hand aneurism, in which the arterial

texture is hardly altered, but merely broken, and in which consequently

its organic sensibility performs but a very small part; on the other,

the osseous incrustations, most of the alterations that are so frequent

in the other textures, are not observed in this.

This texture must be ranked with the cartilaginous, the

fibro-cartilaginous, the fibrous, the muscular even, &c. as it respects

the infrequency of organic alterations. These textures exhibit a

phenomenon opposed to that of the serous, mucous, glandular, dermoid

systems, &c. which are especially characterized by the frequency of

these alterations. Compare the organic properties, the sensibility

and insensible contractility in the two classes of textures; you will

see them very feeble in the first, in which in a natural state, they

preside only over nutrition; you will observe, on the contrary, that

they are very evident in the second, because there they preside over

nutrition, exhalation, absorption, secretion, &c.

The difficulty with which the arterial texture inflames and

participates in the different alterations of the neighbouring organs,

preserves the integrity of the circulation in many cases. What would

become of this function, if the arteries received as easily as the

other textures, the influence of surrounding diseases? Placed at every

moment by the side of inflamed, suppurating, swelled parts, &c. if they

become changed by their neighbourhood, especially in the great trunks,

a general derangement would soon be felt in the motion of the blood.

Dissect the arteries in the organic affections of the stomach, the

liver, the spleen, &c.; they are untouched, and only a little increased

in size; whilst a general swelling seems to confound in a new mass all

the neighbouring textures.

The clots in aneurism adhere sometimes so intimately to the common

membrane, that we are obliged to remove them with an instrument. But

this adhesion is entirely inorganic; it is a kind of agglutination,

that would imply the small degree of life of this common membrane, as

the facility with which colours are fixed in the epidermis implies it

in this last organ.

_Remarks upon the causes of the motion of the red blood._

The red blood is moved in the heart by a mechanism which there is no

difficulty in understanding. But an important question remains to

be decided concerning its motion in the arteries; are these vessels

active or passive in this motion? When the physician examines the

different states of the pulse, is it the state of the heart or that of

the arterial system that he ascertains? From the absence of sensible

organic contractility, as we have observed in this texture, it is

evident that its part would be especially passive; that the motion of

which it is the seat is communicated to it; that the heart is the great

agent of the pulsation of the arteries; that it is that which gives the

impulse, which these vessels only obey, and that consequently in almost

all cases the state of the pulse is the index of the state in which

the vital forces of the heart are found, and not of the state of the

arterial system, whose life is not more raised in the greatest and most

frequent pulsatory motions, than in the feeblest and most infrequent.

Thus in convulsions, the principle of which is a wound, an irritation

of the brain, &c. the nerves, though conductors, are, if we may so say,

passive.

I will now examine in detail this important question, that so many

physicians have considered differently.

_Influence of the heart in the motion of red blood._

1st. The first reason that induces me to believe that the heart is

almost every thing, and that the arteries are particularly passive on

the score of vitality in the motion of the red blood, is the comparison

of the vital forces of these two organs, the astonishing activity

of the organic contractility of the heart, and the absence of this

property in the arteries. In fact, to move of itself, it is necessary

that an organ should have the principle of motion, that is to say,

one of the two kinds of vital contractility in a sensible degree, the

organic or the animal; for we do not know of other vital forces in the

animal organs, and we cannot say that nature has created one especially

destined for the arteries. Grimaud admitted that there was an active

dilatation of the vessels, which opened of themselves, according to

him, to receive the blood, and were not opened by its impulse. We shall

see that this kind of motion is real, to a certain extent, both in the

heart and in the organic muscles. But here it is wholly different;

the heart dilates of itself when it is empty, as we see by drawing it

out of a living animal, and by emptying it afterwards of the fluid it

contains, because it has in itself the cause of its dilatation. But in

no case have I seen the arteries thus undergo an alternate motion when

they are empty. They are uniformly found contracted upon themselves.

2d. If the arteries produce the pulse by their vital contraction, there

ought to be an irregularity in the pulsations below an aneurismal

tumour, since the arterial texture being altered, it loses in part its

contractility, or at least this property is changed. Now we observe

precisely the contrary. On the other hand, every organic disease of the

heart inevitably affects the pulse. Is there an increase of the fleshy

fibres, as in the aneurisms in which the left ventricle is so thick?

it becomes strong; it is irregular, if obstructions exist at the

mitral or aortic valves. If in old age, ossification exists only in the

arteries, the circulation is unaffected; if at the origin of the aorta

or in the heart, it is irregular. An artery might become a bony canal,

and the blood would circulate there as usual, with the difference

only of pulsation. What I have said of the chronic affections of the

heart may be said of the acute ones. Syncope arrests its motion, it

arrests also the pulse. Certain passions, as anger, fear, &c. seem to

be a stimulant to it; they hasten also the arterial motion. All kinds

of inflammation of the pericardium affect the pulse. This membrane

often adheres to the heart in consequence of inflammation, and at

the same time the pleura of both sides adheres to it also; so that

we might say then that the lungs and the heart made but one. I have

seen four examples of this morbid state, in which the motions of the

heart were much contracted; in all the pulse was small, irregular, and

intermittent. The more I open bodies, the more I am convinced that

when the irregularity of the pulse is uniform for a considerable time,

there are almost always organic affections of the heart; from which

there is reason to believe that the irregularities of the pulse that

are acute, if I may use the term, arise from an alteration, not in the

texture, but in the vital forces of this organ, and that the arteries

are almost entirely disconnected with it. We know how frequent these

irregularities are in acute diseases. Since then every alteration of

the heart essentially affects the pulse, and those of the arteries on

the contrary, leave it unaffected, we should certainly conclude from

this, that the one is essentially active in this great phenomenon, and

that the others, on the contrary, are almost passive.

3d. There is no doubt that at the instant a ligature prevents an

artery from receiving the influence of the heart, it ceases to

beat. All the phenomena of aneurisms, treated by compression or by

ligature, establish this fact. If the contrary has sometimes been

observed, it arises only from anastomoses, and then it is equally the

heart that makes the artery beat above and below the ligature. It is

absolutely false, as I have said, that an artery never beats between

two ligatures. Often in aneurism the artery being compressed below the

tumour, this beats much stronger than before.

4th. Cut off the arm of a dead body, and make it pliable by leaving it

for some time in a tepid bath. Fix afterwards to the brachial artery a

small tube; place the other extremity of this tube in the open carotid

of a large living dog; immediately the heart of the animal will drive

blood into the arm. The artery will have a kind of pulsation, less,

without doubt, than in a natural state, but sufficient to be perceived

even through the integuments. I have often repeated this singular and

curious experiment, of which I shall have occasion to speak again. It

was suggested to me by another, of which I have given an account in

my Treatise on the Membranes, and which consists in making the red

blood circulate in the veins, without the motion of locomotion, it is

true, but with a rustling sensible to the finger, and with a velocity

almost equal to that of the arteries. This last experiment alone would

prove that the heart is almost the only agent of impulse of the blood

circulating in the arteries; in fact, every throw of blood coming from

the veins is uniform, because the capillary system pours without a jet

this fluid into these vessels. On the other hand, every arterial throw

is by jets, which are produced by the contraction of the heart. Now if

you open a vein in which you have made red blood circulate by a curved

tube, the throw of blood wall be in jets, which will correspond to the

contractions of the heart. With the difference merely of locomotion,

a vein presents during the circulation of the red blood, the same

phenomena as an artery. Make, on the other hand, the reverse of this

experiment, that is to say, fit a curved tube to a vein and an artery,

so that the blood of the first may flow into the other; the artery will

lose immediately its pulsatory motion, unless it be kept up in the

collateral branches; this does not happen if we select great trunks,

for example, the crural and corresponding vein. It is evident, that

all these experiments, which I have frequently repeated, would give a

result entirely opposite, if the arteries took an active part in the

circulation by their vital properties.

5th. The force of the heart makes the blood circulate through inert

tubes, fixed to the arteries, to a considerable extent. If we cut an

inch of the carotid artery, and substitute a tube fixed to the two open

ends of this artery, the blood will go through this tube and the artery

pulsate as usual above. I cannot imagine in what way those have been

deceived who have obtained different results.

6th. Take two dogs; fix the end of a tube to the carotid of one, on the

side of the heart, and the other end of the same tube to the crural or

carotid of the other, on the side opposite to this organ; the heart

of the first will uniformly make the arteries of the second pulsate,

by sending blood to them. All my experiments upon death, experiments

already published, have shown me this phenomenon. Besides, in aneurism

the pulsation takes place below the tumour; yet at that part, the two

ends of the broken artery are separated; the cellular membrane alone

serves to unite them, by forming the cyst. The blood passes then

through an intermediate body that is not arterial.

7th. Fix to an artery one end of a tube, which has at the other a sac

made of skin, or gummed taffety, the blood will fill it immediately;

then at each contraction of the heart, it will have a sort of

pulsation. It is thus that the aneurismal tumour pulsates, which is

cellular. Whatever may be the organ that contributes to form the cyst,

it would pulsate, provided it received, with the blood, the impulse of

the heart.

8th. I would ask, if the active dilatation of the arteries could be

sufficient to raise the brain, impart a motion to the leg that is

crossed upon that of the opposite side, to overcome the weight of the

tumours that are situated in their course, and raise them at each

pulsation. It evidently requires a more powerful organ to produce these

phenomena, and this organ is the heart.

9th. How is it, that the pulsation of all the arteries is simultaneous,

if a single centre does not preside over this pulsation? The whole

arterial system, struck suddenly with the same blow, is raised and

pulsates at the same time. Is it not evident, that if the arteries

contracted by themselves, the least derangement in one part, the least

pressure, &c. would produce a discordance in the motions?

10th. No animal has arterial pulsations, if it has not a heart, or a

fleshy vessel, knotty, and divided by contractions, as in many insects;

have the pulsations of this vessel, which is a substitute for the

heart, been well observed? It is thus that the system of the vena porta

never has pulsations, though its hepatic part is arranged like the

arteries.

11th. The two ends of a cut artery pour out blood, but this is the

effect of the anastomoses, and not of the re-action of the end opposite

to the heart, as I thought myself for some time. It is for the same

reason that an artery can pulsate sometimes below a ligature.

12th. I have no doubt but that without the heart, the red blood would

have in its great canal, a kind of motion, a motion that would resemble

that of the vena porta; it would be entirely without pulsation.

13th. Cases have been quoted, in which the motion of the arteries

was said to take place as usual, though they contained no blood. I

confess that I do not know how we can be assured of this fact. But if

it was real, it must be placed at the side of that of the soldier, who

could stop the motion of his heart at will. What can we conclude from

an insulated phenomenon, which is in contradiction to all those that

nature daily presents? It may not be useless, I think, to remark, that

since healthy physiology has advanced, has been studied with method, a

love of truth, and a desire only to collect facts, we have no longer

been presented with those extraordinary cases in which nature seems to

depart from the laws she has imposed upon herself.

From all that has been said, it follows, I think, very evidently, that

in the pulsation of the arteries, the heart is almost the only power

that puts the fluid in motion; that the vessels are then passive,

that they obey the motion that is communicated to them, but that

they have none of themselves dependant at least on their vitality.

Thus nature has chosen for the arterial texture one of those of

the economy, in which life is the least evident; as the heart is

remarkable for its vital properties, the arteries are remarkable for

the absence of them. They must be ranked with the cartilaginous,

fibrous, fibro-cartilaginous textures, &c. It is that they may not

disturb the unity of impulse by their motions, that nature has thus

formed the arteries. Suppose that they had the same vital forces as the

intestines; what would become of life? Any convulsive contraction a

little too strong in the aorta or in the great trunks, by contracting

their caliber too much, would arrest the circulation, and produce the

most serious effects by agitating it in an opposite direction to the

heart. In the intestinal canal, this phenomenon only produces vomiting.

It would produce death suddenly in the arterial system. The more

attentively we examine, the more we shall be convinced of the necessity

of having but one agent of impulse for the arterial system, and of

having this system inert, so that it cannot be able to arrest the

course of the blood.

I do not say that the arteries can never contract from the vital

influence; the skin which is not irritable, wrinkles by cold. But the

cases are very rare, in which the arteries contract. When they exist

they cause an inequality of the pulse on the two sides; an inequality

rarely noticed in diseases.

_Of the limits of the action of the Heart._

The heart is then the essential cause of the pulse; it is this which

puts every thing in action in the arterial motion. Many authors have

overrated its influence; they have thought that its impulse was

sufficient to produce, not only the arterial motion, but also that of

the general capillary system, and even that of the veins; so that the

contraction of the left ventricle alone is the cause, according to

them, of the long course the blood runs from it to the right ventricle.

But it is incontestably proved, as we shall see, that when this fluid

has arrived in the general capillary system, it is absolutely beyond

the influence of the heart, and that it moves only by that of the tonic

forces of the small vessels, and therefore for a stronger reason, the

left ventricle has no influence in the venous system. It is in this

respect that the authors, of whom I have spoken, have erred, and not

under that of the impulse that they have admitted in the arterial

system on the part of the heart.

We can, I think, establish nearly the limits of the influence of the

heart upon the blood, by fixing them where this fluid is transformed

from red to black in the general capillary system. As it advances in

the small vessels, the impulse received is undoubtedly weakened, and

the small vessels supply it by their insensible organic contractility;

but I believe that the motion received from the heart, is not entirely

lost until at the place of the change into black blood; so that we

can establish for a general principle, 1st, that in the great trunks,

in the branches and even in the smaller branches, the heart is almost

every thing for the motion of the blood; 2d, that in the ramifications,

it is in part this organ and in part the vital action of the arteries,

which contributes to this motion; 3d, that finally it is this vascular

vital action alone in the general capillary system.

The pulse exists in its fulness, only in the trunks, the branches, and

the smaller branches. It is evidently weakened in the ramifications;

it becomes nothing in the capillary system. The arterial texture

of the great trunks is provided, as we have seen, with insensible

contractility. But the impulse received by the heart is on the one

part so strong, and the column of blood so great, that the influence

of this kind of contractility is really nothing. Irritability alone

could have influence; but this does not exist in the arteries. On the

contrary, in the small vessels, the shock on the one hand impressed by

the heart is insensibly weakened; on the other, the streams of blood

being so fine, they have no occasion for any thing to produce their

motion, except a kind of oscillation, an insensible vibration of the

vascular parietes. It is this that essentially distinguishes the two

kinds of organic contractility. The one is exerted only upon the fluids

in mass, as upon the blood, the aliments, the urine, &c. The other

causes the motion of the fluids when divided into small streams; it

presides over the capillary circulation, exhalation and secretion. The

influence of the first is very considerable wherever there is a great

cavity, as the stomach, the bladder, the intestines; that of the other

takes place only in the small vessels. As long as the blood is in a

considerable mass, the heart must inevitably be the agent of impulse,

the arteries cannot be, from their want of irritability. When it is in

very small streams, then it moves by the insensible contractility of

the vessels. This then is the part which this property performs in the

system with red blood; 1st, it exists in the trunks, the branches and

the smaller branches; but its effect is nothing where that of the heart

is evident. 2d. That of the heart being weakened in the ramifications,

its own contractility begins to have an influence. 3d. Finally, the

heart ceasing to agitate the blood in the general capillary system, the

insensible organic contractility or tone, is the sole cause of motion.

_Phenomena of the impulse of the Heart._

What part then have the arteries in the pulse? The following is what

takes place in this great phenomenon; the arteries are always full

of blood, the impulse that the blood in them receives from the left

ventricle, is felt at the instant in the whole system, and even to

its extremities. Imagine to yourself a syringe, the tube of which

gives rise to an infinity of branches, which afterwards give origin

successively to a number of smaller ones; if, when you push the piston

of the syringe, its body and all the branches and smaller branches

arising from it, are already full of fluid, it is evident that at the

very instant in which the piston shall push the fluid in the body, it

will go out on all sides through the open branches. Now suppose, that

instead of a piston, you could make the parietes of the body of the

syringe suddenly contract, the fluid at the instant of the contraction

would spout out on all sides from these open branches. Another

comparison will render this more evident; strike at one end of a long

timber, the motion will be suddenly felt at the opposite one.

We can from this form an idea of what takes place at the instant of

the contraction of the left ventricle. Authors have spoken of a wave

or undulation of blood, being propagated through the whole arterial

system, and formed by the two ounces of blood that are poured into

the arteries at each contraction. The arterial motion should be thus

considered, if the arteries were empty at the instant of contraction;

but in their state of fulness, the impulse is generally and suddenly

felt, and with almost as much force at the extremities as at the origin

of the arteries; it is only in the ramifications that the motion

becomes a little weakened. Fill with water the arteries of a dead

body, and fix a syringe full at the aorta; at the instant you push the

piston, the water will spout out of the tibial or any other artery, if

you loosen an opening that had been previously made in them.

The idea that is commonly entertained of the progressive motion of the

blood, is wholly incorrect. This fluid has been considered as flowing

in the arteries almost like water in brooks. It is not so. At each

contraction of the ventricle, it experiences suddenly a general motion

that is felt at its extremities. Do you wish for another comparison?

Suppose a syringe, to the tube of which is fitted a series of elastic

pipes arising from each other; push the piston, you will see all these

pipes swell simultaneously, become straight, and the fluid flow at the

same time to the extremities, if they are open.

It is not the contraction of the arteries that drives the blood to

their extremities. This is so true, that if you open one of these

vessels at a distance from the heart, each jet that the blood will make

in going out, will correspond to each contraction of the ventricle. Now

if the arteries drove the blood to all the extremities, by contracting,

their contraction and relaxation would alternate with those of the

heart; but if it was so, each jet of the arterial throw should

correspond to each relaxation of the ventricle; the contrary of this is

the case as I have just said.

From this we see how very inaccurate is the common opinion, which I

believed myself for many years, viz. that the auricles contract at the

same time with the arteries, and the veins at the same time with the

ventricles. The circulation of red blood is thus explained; 1st, the

pulmonary veins drive the blood into the left auricle. 2d. This by

contracting forces it into the ventricle, which dilates to receive it.

3d. This last contracts afterwards, sends it to the aorta which dilates

at the instant of contraction; 4th, then this contracts to drive it to

all the parts. This last does not take place; you can never observe it

like the others, in a living animal. Examine as closely as possible, a

great artery laid bare; it rises, but it does not dilate hardly at all

in an ordinary state, nor does it contract. Contraction of the left

ventricle; general motion of all the arterial blood; the entrance of

this blood into the capillary system, are three things that take place

at the same instant. It is like the blow on the timber, that is felt at

one end, at the same time that it is received at the opposite.

We can form a very accurate idea of the circulation by examining the

mesenteric arteries through the peritoneum, after having opened the

abdomen of an animal; at each pulsation you see them all simultaneously

rise and pulsate at their extremity as well as at their origin.

It is impossible to form an idea of the arterial motion, by considering

the wave or undulation of blood as extending itself at each contraction

in the arteries, and arriving afterwards successively at the

extremities. Read all the authors upon the circulation; you will see

that there is no subject that is treated oftener or more at length,

than that of the course of the arterial blood, and yet there is no one

in which you are left in more doubt and obscurity. Why? because all go

upon a false principle, and all the consequences are inaccurate, where

the principle itself is not correct.

It is not the wave of blood going from the ventricle, that is driven at

each contraction into the capillary system; it is the portion of this

fluid which is found nearest this system, as in the syringe, it is the

portion that is in the tube that the piston forces out and not that

with which it is in contact; whence it follows, that it is only at the

end of some time that the blood arrives from the heart, at the general

capillary system, that it remains during a number of contractions in

the arteries, and that it is only successively expelled; which favours

the mixture of the different principles that compose it.

From this manner of considering the arterial motion, which is the only

real and admissible one, it is evidently impossible that the curves can

injure this motion, besides this is proved by many facts.

I consider also as destitute of every kind of foundation all that has

been said in the books of physiology, upon the causes of the delay

occasioned in the course of the blood, 1st, by its passage from a

narrower to a broader place, and by the conical form of the general

arterial system; 2d, by friction; 3d, by the angles; 4th, by the

anastomoses which give an opposite shock, &c. &c. All this would be

true if the arteries were empty at the time of contraction, because the

blood would then have in them, truly a progressive motion. But in the

general and instantaneous impulse that the whole mass spread in the

arterial system experiences, all these causes are evidently nothing. I

return now to the trifling but very accurate comparison of the syringe.

Suppose that a tube twisted in a thousand ways, with numerous angles,

inequalities, internal projections, &c. was fixed to it; if the tube

and the body of the syringe are full at the instant we push the piston,

the water will escape suddenly from the extremity of this tube with

as much force as if it was straight and short. It is so true that all

the causes of delay, which would have some effect, if the arteries

were empty at the instant the blood is driven into them, have none in

their ordinary state, that many judicious observers, who even admitted

the delay, have seen in their experiments that the motion was every

where the same, in the smaller branches as in the trunks. Why did not

this undeceive them? We know that the pulse is the same in all parts

of the arterial system; how could it be if there was this delay? What

has greatly retarded the progress of the physiology of the circulation,

is the idea that is attached to the velocity of the course of the red

blood. This velocity cannot be rightly estimated, because the motion

is not successive, because, to speak correctly, the blood does not

flow; it is suddenly driven by a general impulse, in which we cannot

calculate any thing.

Philosophers have calculated the motion of fluids, where their

particles are successively displaced, as in the course of a river; but

they have paid less attention to that brisk motion of the whole or of

the mass, if I may so say, that takes place in canals in which they are

enclosed on all sides, and are acted upon at one extremity.

_Remarks upon the Pulse._

Two things are already evidently proved, viz. 1st, that the heart

is the peculiar agent of the arterial motion, and that the arteries

are almost passive in this motion; 2d, that it consists in a general

impulse suddenly experienced by the whole mass of red blood, felt

at the same time at the extremities and in the trunks, and not in a

successive progression of a wave or undulation that goes from the left

ventricle. It remains for me to examine how the heart produces the

pulse by this brisk and instantaneous motion. There is still much to be

elucidated upon this point; but we cannot deny that the locomotion of

the arterial system does much in this phenomenon. At the instant the

mass of blood is driven thus from the heart towards the extremities,

by a motion of the whole, if we may so say, it tends inevitably to

straighten the arteries, especially when they are tortuous. This

straightening necessarily produces a locomotion, which causes the

pulsation of the artery.

As to the dilatation, it is hardly any thing in an ordinary state;

however if you press a little upon an artery, the blood makes an effort

to dilate it and this effort increases the sensation of the pulse;

Jadelot thought that it alone constituted it. On the other hand, if

much blood enters the arterial system at the instant of the contraction

of the heart; if a resistance exists in the general capillary system,

the arteries can be also dilated, but it is not their return upon

themselves or contraction that drives the blood into the capillaries;

this return is subsequent. In fact, at the instant of contraction,

the blood enters on the one part into the arteries in going from the

ventricle, and goes on the other to enter the capillary system; these

two phenomena take place at the same time, since they arise from the

same impulse. Then when there is a contraction in the artery, a motion

which is only the contractility of texture put into action, this

contraction does not drive the blood; but it takes place, because the

blood has been driven into the capillary system at the instant of the

contraction; it is because the artery ceases to be distended, that

it returns upon itself or contracts, and not because it is actually

distended. Hence how the arterial contraction can alternate with

that of the left ventricle; but it is not in the sense that authors

have understood it. There are then two periods in the motion of the

red blood; 1st, contraction of the ventricle; slight dilatation of

the arterial system by the blood that enters it; general locomotion;

passage into the capillary system of a portion of this red blood; all

these phenomena happen at the same time; it is the period when the

pulse is felt; it is that of the diastole. 2d. In the next period,

the ventricle is relaxed to fill itself anew; less full of blood, the

arteries contract a little upon themselves; all take the place they had

lost during the locomotion; this is the period of the systole, a period

purely passive, while some have thought it a very active one for the

arteries.

As but little blood is driven at each pulsation out of the ventricle,

which does not wholly empty itself; and as, on the other hand, at the

same time it enters the arteries it goes out from the side opposite

to the heart, the arterial dilatation and, consequently, contraction,

are almost nothing; thus, they cannot be perceived. Besides, if the

contraction really took place, it would hardly be apparent; for when it

is the contractility of texture that is in action, it produces a slow

insensible motion, a real tightening; whereas contraction, the effect

of irritability is abrupt, instantaneous, and produces a motion that

the eye always distinguishes.

I cannot insist too much upon this fact, which is certain, viz. that

if there is a slight contraction in the arteries at the instant the

pulse ceases to beat, it is not that they have contracted to drive the

blood, but merely that they contract upon themselves, because the blood

that has gone into the capillaries prevents their being sufficiently

dilated; it is contractility for the want of extension. Hence why the

throws of arterial blood going from an open artery, correspond with the

dilatation of these vessels, and the weakening of the throw with their

contraction, which would be entirely the reverse, according to the

common opinion.

The dilatation and contraction of the arteries being almost nothing in

the ordinary state, it appears that the peculiar cause of the pulse

is, as Weitbreck has observed, in the locomotion of the arteries, a

locomotion that is general and instantaneous in the whole system, and

not consecutive, as this author has understood it. I shall not relate

here the proofs of this locomotion; they can be found every where. I

would observe only, that it is so manifest in living animals, that when

we have often examined the circulation by their means, it is impossible

to doubt its reality.

Different causes can make the pulse vary; these causes are, 1st,

relative to the heart, almost the only agent of impulse; thus its

sensible organic contractility, increased, diminished, altered

sympathetically or in any other way, can make it with the same stimulus

contract quicker, slower, or more irregularly than common; thus the

diseases of its organization inevitably alter its motion. 2d. The blood

charged with different natural or morbific substances is a stimulant

more or less capable of putting in play the motion of the heart. 3d.

The general capillary system, according as it receives a greater or

less quantity of blood, or refuses admission to that which the arteries

send there, &c. produces necessarily numerous varieties in the pulse.

There are but few causes relative to the arteries themselves.

If now we consider the great number of causes that can be referred

to these three principal heads, we shall cease to wonder at the

prodigious variety that the pulse exhibits in health, and especially

in diseases. Besides, I shall not examine here in its whole extent

the question concerning the pulse; it is sufficient to have announced

the principles; I shall hereafter develop the consequences, which

are, as we know, of the greatest importance to the physician. We see

by the different views that I have presented, that almost all authors

have described in an inaccurate manner the motion of the blood, and

what loose ideas they have had of it. Experiments have only served to

confuse them; it is a work that requires to be entirely done again,

either with the materials that many respectable authors have already

amassed, especially Haller, Spallanzani, Weitbreck, Lamure, Jadelot,

&c. or with new facts. I have only presented the first bases of this

work.

We have seen how favourable the firm and elastic structure of the

arterial texture is to the locomotion of the arteries, and the

influence the curves of these vessels have upon it. I will add that

the loose union that they form with the neighbouring parts, and their

uniform position in the cellular texture, singularly favour this

locomotion.

If the red blood flowed in the veins, we should feel under the finger

a kind of rustling, instead of the motion of the pulse; this is what

happens in varicose aneurism. There would be no locomotion if the

arterial parietes were made of the dermoid, mucous, serous textures,

&c. there would be different phenomena with the common impulse.

There are then two things in the pulse; 1st, impulse of the blood,

sudden and general motion of its mass by the contraction of the heart;

2d, locomotion of the arteries, an effect produced by this fluid

upon the arterial parietes which transmit it. The first is the most

essential; as to the second, it would vary, if the arterial texture

that produced it ceased to be the same; it depends upon this texture,

and is not essential to the circulation.

When an artery is cut at the end of its trunk, the locomotion is much

less sensible in this trunk, because less resistance is offered there

to the course of the blood.

If an artery is opened laterally, it forms two currents of blood in an

opposite direction, which are driven towards the opening, and which

unite in one throw. One of these currents is direct, the other arises

from anastomoses. It is the same as when an artery is cut, and the

blood flows at both ends.

If an artery is wholly divided, more blood flows from it in a given

time, than passed through it before in the same time to go to the

capillary system, which resisted more. We cannot then judge of the

velocity of the blood by the throw from the open arteries.

_Sympathies._

We have seen that the arteries are rarely the seat of diseases

either acute or chronic, on account of the obscurity of their vital

properties. They can exert then but a very slight influence upon the

other organs; thus, except some sympathetic pains that are experienced

in aneurism, this influence of the arterial texture upon the other

systems is merely nothing. In two or three cases I have seen convulsive

motions produced by the injection of a very irritating fluid in the

arteries. It is easy to distinguish these sympathetic motions, from

those that pain produces in an animal who is struggling to disengage

himself; they are violent tremors or stiffness, like tetanus. It may

be imagined that these experiments should not be made in the carotids,

because the brain, irritated by the injected fluids, would produce

convulsions arising from the stimulant that would be then directly

applied to it, and not from a sympathetic relation. Besides, death

would be the immediate consequence of the experiment, if it was made

upon the carotid.

On the other hand, as the arteries have not sensible organic

contractility, hardly any animal sensibility, and but little tone,

the other organs can with difficulty develop in them sympathies by

their influence; for, in order that a vital property should be brought

sympathetically into action in a part, it is necessary that it should

exist there, and even be conspicuous. Thus the innumerable variations

of the pulse, which are the product of sympathies, have all essentially

their seat in the heart; the arteries are not connected with them.

Now the sympathies make the heart contract or arrest its motion, as

stimulants or sedatives directly applied to it, that is to say, by

acting on its sensible organic contractility. When an aneurism is

broken in a fit of anger, or in the act of coition, a case of which

I have seen with Desault, it is the motion of the blood, which is

suddenly increased, that is the cause of it; it is not the arterial

texture that has been affected by the passion. Besides, upon what

can the sympathies act in the arteries? It could not be either upon

the elasticity or the contractility of texture, the only properties,

however, capable of contracting these vessels. Observe, also, that the

sympathies put in action only the vital properties, because they are

themselves a phenomenon purely vital. The physical properties and the

properties of texture cannot be exercised under their influence; this

is an important observation.

Besides, as the arteries are every where spread in the organs, and as

they form, if we may so say, a part with them, it would be difficult

to distinguish what belongs to them, especially as it respects

sensibility, from what is peculiar to these organs.

ARTICLE FIFTH.

DEVELOPMENT OF THE VASCULAR SYSTEM WITH RED BLOOD.

I. _State of this system in the Fœtus._

The fœtus differs essentially from the infant that has breathed, in

this, that its two great vascular systems in reality form but one,

since the foramen ovale on the one hand, and the ductus arteriosus

on the other, form a direct communication between the two. This

communication is much more evident at the period nearest conception;

these openings contract towards the period of birth. 1st. The foramen

ovale is formed, in the first months, by two productions in the form

of a crescent, whose concave surfaces are opposite, and leave between

them an oval space, which is constantly contracting, because these two

productions constantly approximate and have a tendency to cross each

other, which in fact takes place after birth. 2d. The ductus arteriosus

contracts as the pulmonary artery dilates.

While these two openings are free, which is constantly the case in

the fœtus, the two systems evidently make but one, as I have said;

whence it clearly follows that the blood that circulates there must

be entirely of the same nature, that there cannot be two kinds in the

fœtus, as there always is in the adult. This is, in fact, a remarkable

difference between the two ages. 1st. I have many times dissected small

Guinea pigs in the womb of the mother; their vessels have uniformly

contained the same fluid, which is blackish, like the venous blood of

the adult. This experiment is easy. The abdomen of the mother being

divided, we successively open each of the separate sacs that the womb

has for each fœtus. When one of these sacs is laid open, we cut the

membranes, then the abdomen of the small animal, leaving the umbilical

vessels untouched. The transparency of the parts easily allows us to

see the uniformity of the colour of the blood of the vena cava and

the aorta. The same remark applies to the superior parts. The carotid

and jugular pour out the same blood when they are opened. 2d. I have

three times made the same observation upon the fœtus of a dog. 3d. We

know that the blood of the umbilical arteries is always black; all

accoucheurs have remarked this. 4th. The change of the black blood

to red arises from the contact of air in the lungs; the fœtus not

breathing, cannot then have this kind of blood. 5th. I have dissected

many fœtuses that have died in the womb of the mother; the blood of the

veins and the arteries has appeared to me to be uniformly the same.

It is true that this is not a very conclusive proof, since the mere

standing of the red blood in the vessels, for a considerable length of

time, is sufficient to make it black, as Hunter has observed.

The preceding facts are sufficient to establish incontestibly the

uniformity of the blood in the two systems of the fœtus; an uniformity

that exists at least in external appearance, if it is not real in its

intimate composition. It is for the chemists to elucidate this point.

How is it, that the instant the black blood enters the system of red

blood in the adult, alarming consequences follow, soon asphyxia, then

death, take place, whilst in the fœtus, the black blood circulates with

impunity in the arteries? It is a difficult question to resolve, and

yet these two contradictory facts are equally true. The difference of

the nature of the blood of the fœtus might perhaps serve to remove this

difficulty, if we better understood this difference. In fact, though

the colour assimilates this blood with that of the veins of the adult,

yet it does not appear to be the same; it has an unctuous feel, unlike

the other. It is never found in the dead body coagulated like it,

but always fluid, like the blood of those who have died of asphyxia.

Fourcroy discovered no fibrin in it; he observed that it did not take

the vermilion colour by the contact of the air; that it contained

no phosphoric salts, &c. It is then very probable that if the black

blood is fatal in the arteries of the adult, whilst it circulates with

impunity in those of the fœtus, that it arises from the difference of

the nature of the one and the other. Besides, observe that there is a

very great difference in the functions of the fœtus and the adult. The

first scarcely has animal life; it wants many functions of organic.

The relation of the organs with each other, is of a nature wholly

different from what it will be after birth. No kind of analogy ever can

be established between the fœtus and the infant in this respect. Thus

we have observed that the experiments upon life and death give a result

wholly different in animals with red and warm blood, and in those with

red and cold, which approximate nearly the organization of the fœtus

in some respects. We cannot then establish any kind of parallel in

respect to the injury of the respiratory phenomena, between the fœtus

and the infant, an injury, the causes of which I have sought in my

experiments, since the organization relative to these phenomena differ

so essentially in the one and the other.

Although, as I have said, the blood of the two vascular systems is

confounded in the fœtus, yet there is, especially in the first periods,

a kind of separation in the general mass of blood, a separation that

was first accurately observed by Sabatier, and which is the result

of the arrangement of the foramen ovale and the ductus arteriosus.

This separation divides the mass of blood into two. The following is

the manner in which the circulation of the blood is performed in this

respect.

1st. All the blood that the trunk of the inferior vena cava receives,

either from the capillary system of the inferior extremities, or from

that of the abdomen, or from the placenta by the umbilical vein,

instead of stopping in the right auricle, as in the adult, passes

entire into the left through the foramen ovale, the superior edge

of which is so arranged, that nothing can mix with the blood of the

superior vena cava; so that when we examine attentively, we see that

it is really with the left auricle that the inferior vena cava is

continued. Hence why this auricle is in proportion as much dilated as

the right; for it would be very contracted, if it had only to receive

the blood of the pulmonary veins, the quantity of which is merely

nothing in the first periods of life. From this auricle the blood

passes to the left ventricle, which transmits it to the aorta, where it

meets the carotids and subclavians, which, by numerous ramifications,

carry it to the capillary system of the head and the superior

extremities.

2d. After having remained in this system, the blood returns by the

different branches of the superior vena cava to the right auricle,

where the superior edge of the foramen ovale prevents it from

communicating with the other blood; from this auricle it passes to the

ventricle, which transmits it to the pulmonary artery, which sends

a small part of it that returns to the left auricle by the veins of

the same name, but transmits almost the whole of it by the ductus

arteriosus to the descending aorta, below the origin of the carotids

and the subclavians, which carry the other blood. This is carried by

the branches and ramifications of the aorta to the capillary system

of the abdomen and inferior extremities; the remainder is afterwards

carried by the umbilical artery and lost in the placenta.

It follows from what we have just said, that notwithstanding the

continuity of the two great sanguineous systems in the fœtus, there is

in the first months after conception, a kind of separation of the blood

they contain; that there is even if we may so say, two systems wholly

different from those which will afterwards exist in a separate manner

in the adult.

The first of these systems has, 1st, for origin all the capillaries

of the abdomen, of the inferior extremities, and even those of the

placenta; 2d, for common trunks, below the inferior vena cava, above

the quadruple branch called the aorta; 3d, for agent of impulse the

left side of the heart; 4th, for termination all the capillaries of

the head and the superior parts. The second commences in these last

capillaries, and is composed, 1st, for its trunks, of the superior vena

cava and the descending aorta; 2d, for its agent of impulse, of the

right side of the heart; 3d, for its termination, of the capillaries of

the inferior parts.

The blood is then evidently divided in the first months after

conception into two circulations, which cross, if it may be so said,

in the form of the figure 8, as has been remarked by Sabatier; it is

carried in each, from one assemblage of capillaries to another of the

same vessels. Only instead of moving between the pulmonary capillary

system and the general one, as in the adult, it moves between the

superior and inferior part of this last system; we may then say in this

point of view that the inferior and superior parts of the body are in

opposition in the fœtus, as the lungs in the adult are in opposition to

the rest of the body.

This complete opposition on the part of the circulation, between the

upper and lower part of the body, in the first months of the fœtus,

is probably the origin of the difference that takes place afterwards

between these parts.

All physicians have observed this difference in diseases. If the

median line frequently separates the affections of the right side

from those of the left, the diaphragm seems often to be the boundary

of many diseases. Who does not know, that scorbutic affections appear

particularly below, that serous infiltrations are most frequent there,

and that ulcers are infinitely more common in the inferior extremities,

and that on the other hand, most cutaneous eruptions take place in the

superior parts, &c.? Bordeu, who has said much of the division of the

body into superior and inferior parts, considered one pulse as the

precursor of evacuations from above, and another as that of those from

below, he has however without doubt exaggerated this opposition of the

two parts of the body; still it really exists, and I think that it is

very probable, that the manner of the circulation of the fœtus is the

primary source of it.

After the first months, things begin to change. The quantity of blood

passing by the pulmonary artery was at first scarcely any thing,

because the dilatation of the ductus arteriosus was so great, that it

turned almost the whole of it into the descending aorta. This canal

gradually contracting, the pulmonary arteries dilate, and then more

blood goes through the lungs, and is brought by the pulmonary veins to

the left auricle, which transmits it to the left ventricle, which sends

it to the arch of the aorta; then the mechanism of the circulation

described above begins to change, and approximate that of the infant,

as we shall see.

Still this first mechanism predominates for a long time over the

second; hence it happens that during the greatest part of the time that

the infant is in the womb of the mother, it is the left ventricle that

sends the blood to the superior parts, whilst the inferior receive

theirs by the impulse of the right. Now as the parietes of the first

are evidently thicker than those of the second, and the heart is

further from the inferior than the superior parts, these last receive

a stronger impulse than the others. This perhaps is a new source of

the difference of the two halves of the body; hence nutrition is

more active in that above, hence the degree of vital energy that it

preserves a long time after birth, and which makes it susceptible, the

head especially, of many more affections than the lower half.

As the period of birth approaches, the pulmonary artery sends more

blood to the lungs, and less passes through the ductus arteriosus. For,

as I have said, it is only in a gradual manner that the whole of this

fluid, contained in the body, comes finally at birth to go through the

lungs. Though before it undergoes no alteration there, it does not

circulate the less, which is undoubtedly to habituate it to the passage

that it is constantly to take after birth. The quantity of blood then

is in a direct ratio to the age in the pulmonary artery, and in an

inverse one in the ductus arteriosus.

This arrangement evidently requires a corresponding one in the foramen

ovale; in fact, if in proportion as the ductus arteriosus contracted,

this was not diminished also, all the blood would finally accumulate in

the superior parts. For instead of passing from them to the inferior,

the whole of it would return to them by the left auricle and the

ventricle of the same side. In proportion as the ductus arteriosus

is contracted, the foramen ovale being lessened also, the blood of

the inferior vena cava, the whole of which cannot pass through there,

begins to mix with that of the superior, enters the right auricle,

then the right ventricle, afterwards returns by the lungs to the

left auricle and ventricle and the aorta. What is the consequence of

this? that this artery begins to receive from the left ventricle a

much greater quantity of blood than can pass into the carotids and

subclavians; a portion of it then goes into the descending trunk and is

distributed to the inferior parts.

From what has been said, it appears, that the two portions of the

blood of the fœtus are almost wholly separate in the first months; all

that comes from the inferior vena cava goes into the ascending aorta;

all from the superior passes into the descending, the lungs receiving

scarcely any except by the bronchial arteries for their nutrition. But

as the period of birth approaches, these two portions of blood begin

to mix, and the circulation then has an arrangement between that of

the adult and that of the first months. At birth even, the foramen

ovale and the ductus arteriosus are much contracted, the circulation

goes on in the mother's womb almost in the same way as it does after

birth; the whole difference is that the fluid is of the same nature,

because respiration has not taken place. The sudden change of the

circulation at birth, arises particularly from the introduction of

red blood into the economy. As to the mechanical phenomena, they are

gradually produced by the gradual contraction of the two openings of

communication. The blood gradually ceases to move from the inferior to

the superior capillaries; it then goes from both of these to those of

the lungs and reciprocally.

In considering the circulating phenomena, we err in supposing

that their change is sudden at birth. It is sufficient to examine

the foramen ovale and the ductus arteriosus at different periods

of pregnancy, to see that they contract successively, and that

consequently these phenomena are successive, so that if the fœtus

should remain in the womb a long time beyond its period, and the

contraction should continue in the foramen ovale and the ductus

arteriosus, the blood would circulate as in the adult, from

the pulmonary to the general capillary system exclusively, and

reciprocally. The only difference would be in the uniformity of its

colour, because it would pass through the first system, without coming

in contact with the air.

I do not say that the entrance of the air does not suddenly bring

to the lungs the remainder of the blood which passed by the ductus

arteriosus; but this kind of sudden turn takes place only in a part of

the blood of the pulmonary artery; a part already passed through the

lungs before birth, though the air cells were empty.

In general, there is a constant relation between the quantity of blood

that the right ventricle sends to the lungs, and that which the left

sends to the inferior parts. The more the first increases, the more

abundant is the second; this last evidently exceeds that which goes to

the superior parts. These three things, 1st, the quantity of the blood

of the inferior vena cava which mixes with that of the superior, and

passes with it into the right auricle; 2d, that which from the right

ventricle goes through the lungs and returns to the left auricle;

3d, that which from the left ventricle goes to the descending aorta,

constantly increase as the period of accouchment approaches.

The descending aorta does not undergo by these variations any change in

its caliber; in fact, it is the same thing to it, whether it receives

the blood of the ductus arteriosus, below the origin of the carotids

and subclavians, or whether this fluid comes directly to it from the

left ventricle, through its arch; its parietes constantly increase in

a uniform manner; all depends upon the successive contraction of the

ductus arteriosus and the foramen ovale.

The whole vascular system is generally remarkable in the fœtus for

its great development. The arteries are in proportion larger, which

corresponds with the size of the heart, which is much developed at this

age; it is nearly the same as the nerves in relation to the brain.

The development of the arteries however is not like that of the nerves,

nearly uniform every where. These vessels follow in general the same

order as the parts to which they are distributed. Thus in the superior

parts, the cerebral arteries are much more evident than the facial;

among these, the ophthalmic is more so than the nasal, the palatine,

&c. In the thorax, the thymic arteries are much larger in proportion

than afterwards. In the abdomen, all the gastric viscera being very

considerable, their arteries are already very large; the supra-renal

are much larger in proportion than in the adult. In the pelvis on the

contrary, the arterial system is very contracted, because the viscera

are small, as they receive but little nourishment. In the inferior

extremities, the arteries are a little more contracted in proportion

than in the superior, especially in the earlier periods, for towards

birth, the proportion is nearer equal.

The arterial texture is infinitely more pliable in the fœtus than in

the adult; it will yield more easily to extension; ligatures applied

upon the arteries break it less easily. Aneurisms are extremely rare in

infants.

Many little arteries wind upon the parietes of the great ones in the

fœtus; they are often livid, to see them distinctly, it is necessary,

as I have said, to examine them at this age. Does this abundance of

vessels dispose the arteries in the first age to inflammations, which

are so rare afterwards? I have never observed this alteration.

In the first periods of the fœtus, the layers and arterial fibres are

indistinct; we should say that the coat of the artery is homogeneous.

But it has however much more consistence than most of the surrounding

textures; this consistence corresponds with that of the heart. Destined

to distribute every where the nutritive matter, the arteries ought

necessarily to precede the other organs in their nutrition. This early

growth, always concomitant with that of the heart, would alone prove

that the arteries are made to develop themselves, and that the heart

does not hollow them out, as Haller has said, in the interior of our

organs by the force of its impulse. Besides this mechanical manner of

considering their formation is evidently contrary to the known laws of

the animal economy.

II. _State of the Vascular System with Red Blood during growth._

At the moment of birth, two great revolutions take place in the

system with red blood; 1st, a mechanical one, if it may be so said,

in the phenomena of the course of the blood; 2d, a chemical one, in

the nature of this fluid. The mechanical revolution depends upon the

entire cessation of the passage of the blood through the foramen ovale,

the ductus arteriosus, the umbilical arteries and veins. The chemical

revolution depends upon the formation of red blood. I will now examine

this last.

The fœtus finds at birth that all surrounding objects are the causes

of great excitement; the cutaneous surface, all the origins of the

mucous, are strongly stimulated. The sensations they experience are

even painful, because the difference is very great between the waters

of the amnios and the bodies with which the fœtus comes in contact at

birth, and every abrupt change in the sensations is painful. Habit

soon familiarizes this sensation; but it is not less real at birth,

and it may be said that this moment is as painful for the infant as

the mother. Now, as every lively sensation is generally accompanied

with great motions a general agitation succeeds the impression that the

fœtus perceives from without; all the muscles move, the intercostals

and the diaphragm like the others. The air which already filled the

mouth and wind-pipe, then enters the lungs, and there colours the blood

red, then it is alternately expired and inspired until death. The first

inspiration then is, in this point of view, a phenomenon analogous

to all the motions that the change of external excitement suddenly

produces at birth in the voluntary muscles of the fœtus.

The respiratory motion is, however, too important, since it commences

a new kind of relation between the organs, to depend exclusively upon

this cause. I presume that an unknown principle, a kind of instinct,

induces the fœtus at the moment of birth, to contract the intercostals

and diaphragm. This instinct, which I do not understand, and of which

I cannot give the least idea, is the same that makes the infant the

moment it comes from its mother's womb, contract its lips, as if to

nurse. We certainly cannot say that this motion is an effect of the

very acute external impressions that it feels; these impressions

produce agitations, irregular motions, as if to get rid of these

impressions, and not a uniform motion evidently directed towards

a determinate object. If we examine all animals separately at the

instant of their birth, we shall see that every one performs particular

motions, directed by its instinct. The small quadrupeds seek the breast

of their mother; the gallinaceous animals the grain that is to nourish

them; the small carnivorous birds immediately open their bills, as if

to receive the prey the mother is afterwards to bring to them in the

nest, &c.

In general, it is essential to distinguish accurately the motions,

which, at the instant of birth, arise from new excitements that the

body of the fœtus receives, from those which are the result of a kind

of instinct, of a cause of which we are ignorant. I believe that the

respiratory motion belongs at the same time to the two causes, and more

especially perhaps to the last.

I pass now to the mechanical revolutions of the course of the blood. At

the instant the lungs change to red the black blood that enters them

by the pulmonary arteries, they receive all that which before passed

through the ductus arteriosus; this ceases to transmit any to the

aorta, though, however, it often remains still more or less dilated;

for at birth it is hardly ever entirely obliterated; this contraction

varies singularly at this period. Why does the blood then cease to

flow there? As the aliments do not enter the ductus choledochus, the

lacteal or pancreatic ducts, though they pass their orifices; so

undoubtedly this takes place, because the kind of sensibility of the

ductus arteriosus repels the new venous blood of the fœtus, which comes

no longer from the placenta, because that which the lungs have reddened

will not mix with it. We cannot certainly give any mechanical reason

for its not passing; it really does not, and it evidently depends

upon the vital laws. Besides, the motion of which the lungs become

the seat, the dilatation, and especially the new excitement that the

external air produces there, by rendering considerably more active the

capillary circulation, facilitate that of the two pulmonary trunks, and

give the blood a tendency to pass there rather than through the ductus

arteriosus; it is in this way that the lungs attract, as I have said,

the blood from the pulmonary artery. Does not the great irritation,

of which certain tumours are the seat, draw there more of this fluid?

Is it not on this account that the arteries of these tumours dilate

and acquire a double or even treble caliber? What takes place in these

tumours in a gradual manner, happens suddenly to the blood that still

passes by the ductus arteriosus at birth, and which was very much

diminished, as I have said, by the successive contraction of this canal.

For the same reason that all the blood of the pulmonary artery goes

through the lungs, the foramen ovale is closed; in fact, this foramen

is so arranged at birth, that its valves approximate so as to cross,

as it were; so that when they are pressed against each other, the

communication of the auricles is really closed. Now the red blood

entering the left auricle by the pulmonary veins, pushes the valve of

the foramen ovale corresponding to this auricle, against the other,

and consequently opposes the blood of the vena cava inferior that

endeavours to enter there. This blood flows back to the right auricle.

Now when this contracts to drive the blood into the ventricle, far from

forcing it through the foramen ovale, it necessarily brings the two

valves against each other, and obliterates it. By examining with care

the state of the heart of the fœtus, it is evident that when the blood

enters the left auricle by the pulmonary veins, the right by the venæ

cavæ and the valves are crossed, it is impossible that the blood can

pass them either in contraction or dilatation.

Though the foramen ovale may be open at birth, still the black blood

ceases to pass through it; I say further, oftentimes this foramen

remains open during the whole of life. Many authors have related

examples of this. I have seen a great number, though this assertion may

appear extravagant at first. It is impossible from the arrangement of

its two valves, for the blood to pass through it. When the two auricles

contract at the same time, the blood which is forced by them from

without within, brings the valves together, and thus itself creates

an obstacle to its passage. In the greatest number of cases, the

adhesion of the two valves crossed, is extremely weak; they are rather

in contact than united; so that by forcing between them the handle of

a scalpel, they are easily separated and hardly any traces of rupture

are found. If they were arranged so that the blood could insinuate

itself between them, it would soon separate them and re-establish the

communication. Authors need no longer attempt to explain, how life is

supported when the foramen ovale is open; it is the same as if it was

closed, no more blood passes through it.

The obliteration of the foramen ovale, and the cessation of the passage

of the blood through its opening, are, as we see, phenomena to a

certain degree mechanical. The vital laws perform also, without doubt,

their part on this occasion. Who knows if the sensibility of the left

auricle, stimulated and modified anew by the red blood, does not repel

the black which tries to enter it by the foramen ovale? We see every

day in the economy, fluids passing at the side of openings, without

entering them, though they may be wide, for the sole reason that their

sensibility is not in relation with these fluids. Why does the trachea

convulsively reject all fluids and solids? why does the air alone enter

it? Why does not the blood enter the thoracic duct, which is often

furnished with a valve, as I have observed, incapable of opposing its

passage, and sometimes even has none? Why does the urethra repel the

urine in coition? It is a fault of all authors that they seek only for

mechanical causes in all the phenomena of the circulation. Without

doubt the course of the blood is a mechanical phenomenon; but the

laws that govern this course are vital; it is the same as a bone that

is moved by muscular contraction; the effect is the mechanism of the

lever; the cause is vital.

The blood no longer passing through the ductus arteriosus, this closes

immediately by its contractility of texture; it becomes a kind of

ligament, which fixes to a certain degree the aorta and pulmonary

artery in their respective position. As to the obliteration of the

foramen ovale, it does not arise from this contractility; this

obliteration is not made by a contraction, but by a real agglutination

of the two valves, between which it is obliquely situated at birth.

This agglutination appears to be the effect of a pressure that is made

in an opposite direction, upon the partition between the auricles, by

the blood that each contains. In fact their fibres are so arranged that

they contract from without within; now by contracting thus, they press

from each side the blood against the partition, and consequently the

two valves against each other. Now this agglutination sometimes does

not take place, whilst the contractility is always exerted when the

parts in which it exists cease to be distended; the ductus arteriosus

is uniformly obliterated.

At the same time that the ductus arteriosus and foramen ovale cease to

transmit blood at birth, this fluid is stopt in the umbilical artery

and vein. Why does the blood cease to flow in this artery, though its

diameter continues very large at birth? The principal cause appears to

me to be the nature of the red blood, which is no longer in relation

with the sensibility of this artery. A proof of this is, that if some

time after the fœtus has breathed, respiration is stopt, and the black

blood consequently returns, the umbilical arteries begin to pulsate,

and if the ligature is loosened, they pour out considerable blood.

Baudelocque has frequently observed this.

In general, when respiration is well established, the blood no longer

flows by the umbilical artery, the ligature of the cord is then

useless. On the other hand, when this function is badly performed,

there is reason to fear hemorrhage of this artery. I confess, however,

that there may be other causes for this interruption of the passage of

the red blood. These four things, 1st, the cessation of the entrance

of the blood into the umbilical vein; 2d, interruption of the passage

of that of the inferior vena cava by the foramen ovale; 3d, of that

of the pulmonary artery by the ductus arteriosus; 4th, of that of the

descending aorta by the umbilical artery; these four things, I say, the

three last especially, appear to depend upon a cause that we do not yet

understand. The change of the relation of the organic sensibility with

the nature of the blood, is perhaps only accessory, since, as I have

observed, it is less this property than the action of the heart itself,

which is the cause of the circulation in the trunks. This subject

deserves the most attentive examination of physiologists.

Respiration being once well established, the lungs are in opposition to

the whole body; it sends blood to all the parts, and they all send it

to the lungs. The boundary is then rigourously established between the

system with black blood and that with red, and things then go on as we

have before described.

After birth the vascular system with red blood predominates for some

time by its greater development and its more numerous branches, in

fact the red blood enters more parts then than it does afterwards.

It is sufficient to dissect living animals of different ages, to be

convinced of the greater quantity of blood in young animals, that the

system contains, of which we are treating; so that, as I have said

elsewhere, the two opposite ages of life exhibit an inverse arrangement

as it respects the fluids and solids. The first are much more abundant

towards the period of conception. The second always predominate more

towards the last age.

The predominance of the system with red blood remains evident to the

end of the period of growth. We see the necessity of this predominance

to distribute to all the parts the materials of their nutrition and

growth; in fact, in the adult the arteries contain only what is

destined to the first. In the infant, they contain moreover what

is destined to the second. Hence the caliber of the arteries is

proportionably larger than afterwards, in order to contain more fluid.

Injections demonstrate this; and on this account small subjects are

not less favourable for the study of the arteries, than of that of the

nerves. These vessels are more prominent in them; only the surrounding

parts being less developed, we cannot see the connexions so well.

In proportion as the infant advances in age, the equilibrium is

gradually established in the system with red blood. In the head,

the facial arteries are more evident, and come gradually in their

development to the level of the cerebral. In the thorax, the thymus

diminishing as the lungs increase, their nutritive arteries follow

an inverse order; the bronchials dilate and the thymic contract. In

the abdomen less blood goes to the capsular arteries; but most of the

others receive as much of it. The pelvis and the inferior extremities

have more of it, and their development is proportionably evident.

III. _State of the Vascular System with Red Blood after growth._

It is about the period of puberty that the increase in height ceases;

the increase in thickness continues always. The genital parts, hitherto

without influence, seem to be then a centre of more active vitality

than most of the other organs. The portion of the system with red blood

that belongs to them, then becomes greater. The first effect that

results from it is the secretion of semen, and a general impulse of the

individual towards new tastes and desires, towards those relative to

the propagation of the species.

Another phenomenon is soon the consequence of this. As the lungs are

connected in an intimate, though unknown manner, with the genital

parts, they acquire also a predominance with them. Their vital energy

is increased, and then begins the period of the affections of this

viscus; then, the cause that would in the adult produce a gastric

affection, brings on a pulmonary one.

It is truly only at this period, that the predominance of the superior

parts, of the head especially, ceases entirely. Thus whilst in infancy

the nose is frequently the seat of hemorrhage, in youth it takes place

particularly from the lungs. We may consider the increase of the energy

of the lungs, which happens shortly after puberty, as the termination

of the predominance of the superior parts. The cutaneous eruptions of

the cranium, tinea capitis, &c. cease to be as frequent. Convulsions,

and all the diseases that arise from the extreme susceptibility of the

brain, become also more rare, and seem to give place to a great number

of acute pulmonary affections.

It is towards this period, that is, some time after the end of

the increase in height, that the diseases that are considered as

the product of an arterial plethora, begin especially to manifest

themselves; this may be said to be their age, and it arises from the

following cause; as the blood contains before puberty, not only the

materials of nutrition, but also those of growth, and whilst this

continued the whole is expended in the system with red blood. But when

the parts cease to increase in length, if this system still continues

to receive the materials of growth, a true arterial plethora takes

place. About the end of growth generally, some affections appear that

indicate a predominance of the blood; as this is however under the

influence of temperament, of the mode of life hitherto led, of the

season and a thousand other causes, which, making the phenomena of the

animal economy vary, rarely permit us to establish exclusive general

principles. Thus all that is said upon the disposition to different

diseases, in the different ages, &c. is subject to many exceptions.

The predominance of the lungs is gradually lost; the equilibrium is

established among all the organs, which, hitherto had each performed

a part more or less conspicuous in the phenomena relative to the

different ages. As the system with red blood is uniformly, in every

part, in proportion to its growth, to which it especially contributes,

the equilibrium is in that way established between the different

parts at twenty-six or thirty years of age; all the arteries have a

proportional size, analogous to what they will always have afterwards.

Whilst until then, some predominated, according to the predominance of

the growth of the organs to which they are sent.

Towards the fortieth year, the gastric viscera seem to acquire a more

decided vital activity; but this activity has no influence upon the

size of the arteries that are distributed to these viscera.

Though the growth in height may end about the sixteenth or seventeenth

year, that in thickness uniformly continues; so that the internal

viscera still grow, and their arteries consequently enlarge, until

the last growth ceases. This phenomenon has constantly struck me, in

comparing arteries injected in subjects from sixteen to twenty years,

with those in subjects beyond thirty-six or forty. In the last they are

uniformly larger. It is this difference that first gave me the idea

of distinguishing growth, into that in height, and that in thickness.

For the development of the arteries is the constant index of the state

of the growth of the organs. The period of the cessation of growth in

thickness is then remarkable, 1st, by the cessation of the increase of

the caliber of the arteries; 2d, by the general equilibrium that is

established in their development.

As the arteries grow in the years that succeed the end of the growth

of the body, they increase in compactness and thickness. Their fibres

become more evident; their elasticity increases; their pliability is

lessened; hence why the age of the adult is that of aneurisms. Observe

that the density of the arteries follows, in its augmentation, the same

proportion as the fleshy fibres of the heart; so that as this is more

able to send the blood with force, these are more able to resist it.

IV. _State of the Vascular System with Red Blood during old age._

In the last years, the system with red blood is remarkable for the

following phenomena.

The number of the arterial ramifications is much diminished. As the

heart loses its energy, it sends less blood, and with less force. The

general vibration that it produces in the whole arterial tree, is less

felt at the extremities of this tree. The small vessels that form

these extremities gradually contract, are obliterated and become so

many little ligaments. Hence why, when the periosteum is separated from

the bone, the dura mater from the internal surface of the cranium, only

a few drops of blood escape; why the skin, having hardened like horn,

no longer exhibits the rosy tint of the preceding ages, especially of

youth; why the section of a bone does not furnish hardly any blood,

whilst it was so abundant in the fœtus; why the mucous surfaces look

pale, the muscles have a dull colour, &c. All anatomists know that

injections succeed less in proportion, as the subjects are more

advanced in years; that in extreme old age the trunks alone are filled;

that the fluids never enter the ramifications; that it is the reverse

in young subjects; that even coarse injections oftentimes so fill the

ramifications, as to render dissection difficult. I have dissected

many old living animals; and the small quantity of blood their vessels

contain compared with those of young animals is very remarkable. The

general proposition that I have established, viz. that the solids

are constantly acquiring the predominance, is perfectly true. This

obliteration of the small vessels is remarkable even upon the parietes

of the great vessels; we see it in the dead body; I have observed it in

the living.

The less quantity of red blood that is found proportionably in old age,

is referable especially to the state of nutrition, which is merely

nothing when compared with that of infancy. Observe also, that united

with the weakness of the motion that animates the blood, it is a cause

of the small degree of excitement which the parts have in old age. In

fact the use of the circulation is not only to carry to the different

parts the materials of the secretions, of exhalations, nutrition,

&c. we shall see that it keeps them also in a state of constant

excitement by the shock it gives them at its entrance, a shock, the

principle of which is evidently in the heart. Now this shock is in a

ratio compounded, 1st, of the quantity of the fluid; 2d, of the force

with which it is sent. In both respects, the excitement constantly

diminishes, as age advances. Observe also that all the functions of the

infant, both organic and animal, are characterized by a vivacity and

impetuosity that form a remarkable contrast with the slowness and want

of energy of those of old people.

The arterial texture always becomes more and more condensed as age

advances. The layers that form the fibres of the peculiar membrane

become drier, if I may be allowed the expression.

I have said that the internal membrane is very often the seat of a

kind of peculiar ossification, which has hardly any influence upon the

circulation, except when it is seated at the origin of the aorta.

The caliber of the arteries does not dilate in old age. There is

scarcely any except the arch of the aorta, which constantly undergoes

an enlargement more or less considerable, which is always without

rupture of the fibres, consequently supposes an extensibility of these

fibres, and undoubtedly depends upon the habitual and direct impulse

that the blood exerts against the concave side of this curvature. I

have often examined to see if there was a similar dilatation at those

places in the arteries where the curves are very evident, in the

internal carotid, for example, at the place where it passes through the

carotid foramen; I have not discovered any.

In the last periods, the pulse is remarkable for its extreme slowness;

a phenomenon opposite to that of infancy, in which the blood moves with

great quickness. These two opposite facts are, after what we have said,

foreign to the arteries. They indicate only the state of the forces of

the heart, which is the agent of the general impulse of the red blood.

It is the same of the pulse in the last periods of life. It is not a

real pulsation of the arteries; it is a kind of undulation, of weak

oscillatory motion, and the more obscure, as life is more feeble. Now

I am convinced that the heart alone is the agent of this undulation; I

am convinced of it by the following very simple experiment. I have laid

bare in many dogs, on one hand the carotid, on the other the heart by a

section of one side of the thorax, made in such a manner that the other

can still perform respiration. By placing the finger upon the artery,

I observed that as long as the heart beat by a sudden impulse, that

the pulse was kept up as usual, that it was even accelerated, because

the contact of the air increased the quickness of the contractions of

the heart; but at the end of a little time, this organ began to be

weakened in its motions, then it contracted by a kind of general tremor

of its fibres. In proportion as the weakness of the motions of the

heart increased, the pulse was successively weakened. Then when the

tremor extended to all its fibres, the pulsation of the artery changed

to a kind of undulation, of feeble oscillation, the precursor of the

cessation of all motion.

I shall observe, under the system of the muscles of organic life,

that the heart has many kinds of contraction. The principal are, 1st,

that which it ordinarily has, in which there is a contraction and a

dilatation that succeed suddenly and regularly; 2d, that in which

these two motions, retaining their natural character, are irregularly

connected; 3d, those in which the fibres only oscillate, and by which

the cardiac cavities a little contracted, communicate to the blood

a less sudden shock, a general tremor, an undulation, &c. Now with

each kind of motion of the heart, there is a peculiar pulse that

corresponds. It is easy to be convinced of this upon living animals.

I am astonished that authors who have disputed so much upon the cause

of this phenomenon, have not thought of having recourse to experiment

to elucidate the question. There are undoubtedly many modifications in

the pulse, whose coincidence with the motions of the heart could not

be perceived; but that of the slow and frequent pulse, the strong and

weak, the intermittent, undulatory, &c. can be immediately discovered,

by laying the heart bare and placing the finger at the same time upon

the artery. We see then uniformly, during the moments that precede

death, that whatever may be the modification of the arterial pulsation,

there is always an analogous modification in the motions of the heart;

this certainly would not be the case, if the pulse depended especially

upon the vital contraction of the arteries. I have had occasion to make

these experiments many times, either directly for this object, or with

others in view; I have seen the motion of the heart always correspond

with that of the arteries. In general the theory of the pulse requires

as I have said, new researches; but I have facts enough upon this point

to be convinced that the varieties it undergoes in the different ages,

as under other circumstances, depend almost exclusively upon the heart,

which produces in particular this kind of undulation, of oscillatory

motion which is between the pulsation of the natural state and the

complete cessation of this pulsation.

V. _Accidental development of the System with Red Blood._

I shall speak under the organic muscles, of the accidental development

of the left portion of the heart. As to the arteries, new ones are

never formed; but oftentimes, those that do exist acquire a remarkable

size; this depends on two causes, 1st, on an obstruction to the course

of the blood; 2d, on the growth of any tumour.

1st. The dilatation of the arteries by an obstruction to the

circulation, is evident in the ligature of aneurismatic arteries, in

the spontaneous cure of aneurisms, a phenomenon of which within a

few years a great number of examples has been published, &c. Then,

sometimes the great collaterals increase in size, sometimes their

caliber remains the same, and it is by the ramifications that the

communications are made. As the branches dilate, their thickness

increases in proportion with their breadth; at least I have twice

observed this fact, which is analogous to that which the left ventricle

presents when it becomes aneurismatic.

2d. All tumours do not produce a dilatation of the arteries; we see

this dilatation in cancers, in those of the breast, of the womb, &c.

in osteo-sarcosis or spina ventosa, in the different fungi, &c. In

general, most tumours that give great pain to the patients exhibit this

phenomenon. We should say even that pain in a part is sufficient to

attract there habitually more blood, and dilate the arteries; we know

that in the operation for lithotomy, when the patients have previously

suffered much, hemorrhage is often more to be feared.

After long and copious secretions or exhalations, I have not observed

that the arteries were more dilated in the glands or around the

exhalant organs. How large soever the cysts may be, their parietes

never contain arteries proportioned to those that are developed in

cancerous tumours. The cerebral in hydrocephalus, the mediastinal,

intercostals, &c. in hydro-thorax, the mesenteric, the lumbar, the

stomachic, the epigastric, &c. in ascites, the spermatic in hydrocele,

the renal in diabetes, the branches that go to the parotids after

a long salivation, retain their ordinary size, and under some

circumstances they become even smaller.

When the arteries dilate in tumours, do their parietes thicken in

proportion, as in the preceding case? I have no data, from which I

could determine this point.

VASCULAR SYSTEM

WITH BLACK BLOOD.

The red blood circulates in a single system, the branches of which

every where communicate. The black blood on the contrary is contained

in two separate systems, which have nothing in common but the form, and

which are, 1st, the general system; 2d, the abdominal. We shall now

examine the first, and afterwards the second.

The general vascular system with black blood arises as we shall see,

from the whole of the great capillary system, is collected towards the

heart in great trunks, and terminates in the pulmonary capillaries. As

the portion of the heart that belongs to it will be examined hereafter,

and the pulmonary artery, by its peculiar membrane, has great analogy

with the peculiar membrane of the other arteries, we shall now

particularly examine the veins; but we shall describe in a general

manner, the common membrane that is spread upon the whole system with

black blood.

ARTICLE FIRST.

SITUATION, FORMS, DIVISION AND GENERAL ARRANGEMENT OF THE VASCULAR

SYSTEM WITH BLACK BLOOD.

We shall now examine the veins as we have the arteries, in their

origin, course and termination. Only we shall do it inversely, to

accommodate our ideas to the course in which the blood flows in their

channels.

I. _Origin of the Veins._

This origin is in the general capillary system. I shall point out in

this system, how the veins are continued with the arteries. I would

only remark here that these vessels never arise from any organ that

the arteries do not enter, as the tendons, the cartilages, the hair,

&c.; which evidently proves that the blood is not formed in the general

capillary system; it leaves there the principles that made it red, it

perhaps acquires there new ones; it is modified in fact, but never

created.

It is not as easy to distinguish accurately the veins at their exit

from this system, as it is the last arteries at their entrance into it,

because the valves prevent injections from penetrating so far. It is

in subjects that have died of asphyxia, apoplexy, &c. that the venous

ramifications can be best observed. We see then that they are soon

divided into two orders; one accompanies the last arteries, the other

is distinct from them.

In the greatest number of organs, venous branches go out at the same

place that the arteries enter. There are however some exceptions to

this rule. In the brain, for example, the arteries enter below, the

veins go out above. In the liver, the first enter below, the others go

off behind, &c. This circumstance is, in general, indifferent to the

circulation, which goes on the same whatever may be the relation of

the arteries with the veins. In those places where the small veins go

out at the same time that the small arteries enter, sometimes more or

less of cellular texture serves to unite the small vessels that are in

apposition, sometimes there is a space between them, as in the muscles,

the nerves, &c.

Besides the venous origins corresponding with the arterial

terminations, there is an order of veins which is separated from

the arteries at the exit from the capillary system. This order is

particularly remarkable at the exterior of the body. We see that all

the organs that are found there furnish, 1st, veins that go to the

interior to accompany the arteries; 2d, others that go to the exterior

to become sub-cutaneous, and to form trunks of which we shall soon

speak. In many internal organs, the same venous division is observed.

It follows from this general arrangement, that many more veins go from

the capillary system than there are arteries that enter it. This is the

principle of the disproportion of the capacity existing between the

system with red blood, and that with black, a disproportion of which we

shall soon speak.

The veins at their origin frequently communicate among themselves. We

see many little spaces that arise from their interlacing, in the places

where they can be seen, as under the serous surfaces, &c.

II. _Course of the Veins._

At their exit from the general capillary system, as we have just

said, the veins are differently arranged. 1st. In the extremities

and external organs of the trunk, they form two sets, the one

interior, which accompanies the arteries; the other exterior, which is

sub-cutaneous. 2d. In the internal organs we frequently make a similar

observation; thus there are superficial veins of the kidney, and deep

ones, that accompany the arteries; but oftentimes all the veins unite

themselves to those that follow the artery.

The cutaneous portion of the veins is very remarkable in the

extremities, where there are considerable branches, viz. the saphena

in the lower, the cephalic, basilic, and their numerous divisions

in the superior. In the trunk and the head, we do not see any great

sub-cutaneous branches, except the external jugular in the neck; but

there is a number of smaller branches proportioned to the minuter ones

that are distributed there.

The external parts, then, are remarkable by the predominance of the

trunks with black blood over those with red. Oftentimes these trunks

can be traced through the integuments, upon which they show themselves

much more than those that are whiter and more delicate; they have,

besides, no connexion with the tinge that colours them, which arises

from the blood contained in the general capillary system.

In the interior of the body, the veins almost every where accompany

the arteries; they follow the same distribution; so that they are not

commonly described, because the course of the arteries is sufficient

to represent theirs. Usually a common cellular space receives both the

trunks of the two sorts of vessels and those of the nerves. Sometimes,

however, the veins are separate, as the azygos, for example, which has

no corresponding arterial trunk, and which on this account requires in

descriptive anatomy, like the superficial ones of the trunk and the

extremities, a particular examination and an accurate dissection to

obtain an idea of it.

The deep-seated veins have a caliber much more considerable than

that of the arteries; most usually they are more numerous, as in the

extremities, where each artery is almost always accompanied by two

veins.

III. _Proportion of the capacity of the two systems with Black and Red

Blood._

After the observation I have just made upon the origin and course of

the veins, it is evident that their sum total has a capacity much

greater than that of the arteries. This assertion it is easy to prove

in detail, wherever there is an artery and vein united, as in the

kidneys, the spleen, the extremities, &c.; where the arteries are

separate from the veins, as in the brain, the liver, &c. it is not

less sensible. Finally, there is, as I have just said, a division of

sub-cutaneous veins, which is evidently one more than the arteries have.

Many physiologists have endeavoured to calculate the relation of

capacity between the two systems with black and red blood; but this

relation varies too much ever to be the subject of any calculation.

Is it upon the dead body that the attempt is made? But the veins will

be more or less dilated according to the kind of death; in apoplexy,

asphyxia, drowning, &c. they have a diameter almost double that which

they exhibit when the subject has died of hemorrhage, because the first

kind of death accumulates much blood in the veins, and the second

deprives them of it. We can give a greater or less capacity to the

veins of an animal, according to the manner in which we kill him, as

we can enlarge or contract the right cavities of the heart by similar

means. You can never find the veins exactly equal in any two subjects,

though there may be a great resemblance as to size, age, &c. Is it

upon a living animal that the attempt is made? But, besides its being

very difficult, you will not then have a result uniformly applicable,

because the veins vary in diameter as they are more or less full.

Examine these vessels in subjects in whom you can see them by the

transparency of the integuments; sometimes they are more, sometimes

less apparent; their size sometimes appears double, at others, hardly

distinguishable. Certainly after drinking copiously, by which the black

blood has received a great augmentation of its fluid, the vessels

are more dilated than in an opposite state. The veins are remarkably

contracted after death from hunger. I have often observed the same

phenomenon in dropsies, phthisis, marasmus, &c. Always when the mass

of blood is diminished, the veins contract by their contractility

of texture. The arteries are infinitely less subject to variations

of diameter, on account of their firm and compact texture, though,

however, they show much of it.

Let us reject, then, every kind of calculation upon the proportions

of capacity of organized canals. We can only calculate what is fixed

and invariable; but that which varies at every instant can only be

the object of general assertion. Besides, of what importance are the

rigorous proportions that some physicians have endeavoured to establish

between our parts? They are nothing in the explanation of the phenomena

of health and disease. Let us, then, be content with this general

assertion, that the venous capacity surpasses the arterial. It may be

said, that in a given time there is more blood in one than the other.

The same observation applies to the two sides of the heart, one of

which belongs to the same system with the veins, and the other to the

one with the arteries. The right has commonly a greater capacity than

the left, not precisely under the relation of the fleshy texture, but

under that of the fluid that distends it; this is so true, that if in

an animal whose thorax is opened, the blood is made to accumulate in

the left side by ligatures, and the right is emptied by puncturing

it, the last will be less in size than the first. Always when we find

it larger than the other in the dead body, except in diseases of the

heart, it is because it contained more blood at the moment of death; in

fact, as this fluid ordinarily stops first in the lungs, it flows back

to this side of the heart, which is almost always the largest.

This is the great difference between inert cavities and those that

possess life, viz. that these last can change their capacity every

moment, whilst the others remain always the same. In the living animal,

the right side of the heart has almost always a greater capacity than

the left, because the quantity of blood it contains is greater.

There are, then, two things generally true, viz. 1st, that the great

tree that terminates the system with red blood is in general of less

capacity than the great tree that commences the system with black

blood; 2d, that the same observation is applicable to the two sides of

the heart, which correspond with these two trees.

As to the tree that terminates the system with black blood, compared

with that which commences the system with red blood, the same thing

does not hold true. The pulmonary artery and the veins of the same

name exhibit a disproportion of capacity, less it is true, than in

the other parts, a disproportion which is real, however, and which,

notwithstanding what many authors have said, is in favour of the veins.

How does this happen? it would seem that since the one is continuous

with the veins and propels the same fluids, it ought to have the same

proportion of diameter; and that since the others are continuous with

the arteries, that they also should be in proportion to them. This

arises from the difference of the velocity of the blood; in fact, this

fluid circulates quicker in the pulmonary artery than in the veins

of the same name, since it has the impulse of the heart, which these

last want; then, in a given time, as great a quantity of blood passes

through it, though the diameter of this artery is smaller; what do I

say? if it was equal, the circulation could not go on. In the same way,

if the aorta equalled in capacity the two venæ cavæ and the coronaries

united, and the blood had the same velocity there, the circulation

would cease.

The four pulmonary veins united are a little larger than the aorta,

which, however, transmits all the blood received from them. Why?

Because the impulse that the left ventricle communicates, makes, in a

given time, more blood pass by the aorta than by the four pulmonary

veins. These two things, 1st, the velocity of the fluid; 2d, the

capacity of the cavities in which it circulates, are then in an inverse

order in the two opposite trees that form each vascular system. In that

with red blood, there is less velocity and greater capacity from the

pulmonary capillary system to the agent of impulse; and from this agent

to the general capillary system, there is, on the contrary, greater

velocity and less capacity. In the vascular system with black blood,

there is less velocity and greater capacity from the general capillary

system to the agent of impulse; and from this agent to the pulmonary

capillary system, there is more velocity and less capacity. Without

this double opposite arrangement, it is evident that the circulation

could not take place.

There is, however, a remark to be made upon this subject; it is, that

the capacity of the four pulmonary veins united, is not so much larger

than the aorta as that of the venæ cavæ and the coronary is than the

pulmonary artery; and this is the reason of it; as the pulmonary

veins run a very short course, the impulse, on the one hand, that

the red blood has received from the pulmonary capillary system, is

preserved there more; on the other hand, this fluid is there free from

numerous causes of delay that the blood experiences in the venæ cavæ

and coronaries; then the velocity is greater there, and the capacity

should be therefore less. If the lungs were situated in the pelvis, the

pulmonary veins would certainly have a greater capacity, because having

a greater extent to go over, the velocity of the blood would be more

retarded.

We can easily understand now the cause of many arrangements that have

engaged the attention of anatomists; viz. 1st, why the sum of the

arteries coming from the aorta has less capacity than that of the veins

going to the right auricle; 2d, why the four pulmonary veins surpass

also in diameter the artery of the same name; 3d, why these four

veins are not exactly in proportion with the aorta, which is really

a continuation of them; 4th, why the venæ cavæ and coronaries are so

disproportioned to the pulmonary artery, which is, as it were, their

continuation.

If there was no agent of impulse in the two systems with red and black

blood, their capacity would be every where nearly the same, because

the velocity of the fluid would be every where nearly the same. This

is precisely what happens in the system with black abdominal blood, in

which the hepatic portion of the vena porta is nearly as large as the

intestinal one, because there is no heart between the two.

The velocity is less in the general veins and in the pulmonary, because

they have not at their extremity an agent of impulse; we see there

only a capillary system. The opposite reason explains the velocity of

the course of the blood in the general arteries and in the pulmonary.

We have seen in the preceding system, that the presence of an agent

of impulse at the origin of the two great arteries, requires there a

considerable resistance of this texture, whilst the absence of this

agent requires but little resistance in the veins.

We see, then, clearly, why these three things, 1st, weakness of the

parietes; 2d, slowness of the motion; 3d, great capacity, are the

attributes of the veins with black and red blood; why these three

opposite things, 1st, strength of the parietes; 2d, velocity in

the motion; 3d, less capacity, characterize the arteries of both

sanguiferous systems.

We see also from this why, though the red and black blood form in their

whole course a continued column, though the common membrane over which

they pass may be in the whole extent of each system nearly the same,

the organs exterior to this membrane are, however, very different.

The inverse ratio of the velocity of the motion with the capacity of

the vessels, appears to me so evident, that we might be able to judge

nearly by the inspection of the vessel of the velocity of the blood

that runs through it, if many causes did not, as I have said, make the

vascular parietes vary at the moment of death. We know that all the

causes that lessen in the veins the velocity of the blood, increase

their capacity; it is thus that we make them prominent by ligatures;

that pregnancy enlarges those of the inferior extremities, that

long-continued standing produces the same effect, &c.

It is to the same reason that must be referred the explanation of the

following phenomenon; viz. that the relation of the arteries and the

veins is not every where the same; thus the renal, bronchial, thymic

veins, &c. are in general smaller in proportion to their arteries, than

the veins of the spermatic cord in proportion to the artery of the same

name, than the hypogastric veins in proportion to the corresponding

artery. The blood has less difficulty in circulating in the first than

in the second, where it rises against its weight; hence why the veins

of the inferior parts, especially at a certain age, surpass their

arteries more in diameter, than those of the superior parts exceed

theirs.

_Ramifications, Small Branches, Branches, Angles of Union, &c._

The veins present in their course, as it respects branches, smaller

branches and ramifications, an arrangement analogous to that of the

arteries, except that it takes place inversely. The ramifications are

nearest the origin; they soon unite into smaller branches, these into

branches, and these last into trunks.

The ramifications and most of the small branches are found in the

interior of the organs. The first make an integral part of these

organs, and are between their fibres, &c.; the second lie in their

great interstices; in the glands between the lobes, in the brain,

between the circumvolutions, in the muscles between the fasciculi, &c.

In going out of the organs, the small venous branches run into

the branches, which take, as we have seen, two positions, one

sub-cutaneous, the other deep. The sub-cutaneous branches go in the

extremities between the aponeurosis and the skin, in the trunk between

this and the cellular layer that covers the muscles. The deep branches

lie in the interstices that the organs have between each other,

accompanying almost every where the arteries. The cerebral branches

have a peculiar arrangement; they are placed in the interstices of the

dura mater, and form with them what are called sinuses.

The venous branches differ from the arterial in this, that they are

infinitely less tortuous; this is remarkable under the skin and in

the interstices of the organs. This is a reason that would prevent

locomotion, supposing that there was an agent of impulse at the origin

of the veins, and that their parietes were not so loose. Hence a series

of arterial tubes is really longer than a corresponding series of

venous tubes; this facilitates the motion of the black blood, which has

a less extent to go over, and which besides would find causes of delay

in the curvatures, greater than the red blood, because this is driven

by a strong agent of impulse, and the other is not.

The venous branches unite to form a certain number of trunks that are

connected with those that are immediately discharged into the right

auricle; these trunks are the internal jugulars, the iliacs, the

azygos, the subclavians, &c. They are still less tortuous than the

branches; they have, like the arterial trunks, deep positions, far from

external agents, from which many organs defend them, as a hemorrhage

from them would be followed with serious consequences.

The trunks, branches, smaller branches and ramifications do not always

arise necessarily from each other, in the manner we have just pointed

out. The branches are often united to the trunks, the ramifications to

the branches, &c. &c.; as it is with regard to the arteries.

The angles of union vary; sometimes they are right angles, as in the

lumbar, renal veins, &c.; sometimes they are obtuse, as in some of the

intercostals; most commonly they are acute.

The arrangement of the smaller branches and the branches is as variable

at least in the veins as in the arteries; they partake, in this

respect, of the general character of irregularity that the organs of

internal life exhibit. It is necessary only to attend to the general

position and distribution of the branches, smaller branches, &c. Their

union with the trunks and among themselves, is different in almost

every subject.

_Forms of the Veins._

The same observation may be made upon the forms of the veins as upon

those of the arteries.

1st. A trunk, branch, &c. are cylindrical, when examined in a space

where they receive no branch. In the dead body they appear flat, which

arises from the collapse of the parietes, and this is owing to the

absence of blood. But by distending them with air, water, &c. they take

their primitive form. In the living body they appear round.

2d. Examined in a considerable extent, a venous branch appears conical,

so that the base of the cone is towards the heart and the apex towards

the general capillary system. This form arises from the smaller

branches, that are successively united to this branch, and increase its

capacity as it approaches the heart.

3d. Considered as a whole, the venous system represents three trunks;

one corresponds with the vena cava superior, another with the vena cava

inferior, and the third with the coronary vein; these three trunks

have their apex at the auricle and their base at the general capillary

system. Anatomists thus represent the whole of the veins, because the

sum of their divisions, like the arteries, has a greater capacity than

the trunks from which these divisions arise.

There is however an observation to be made upon this subject, and

that is, that the relation between the trunks and their divisions is

not as exact in the veins as in the arteries; thus the sum of certain

divisions considerably surpasses their trunks, whilst this relation

is infinitely less in other cases. But all this arises still from the

extreme variation of the venous parietes, according to the quantity

of blood they contain; thus in dead bodies, sometimes the branches

are much dilated by this fluid, and the trunks remain the same;

sometimes an opposite phenomenon is observed. 1st. This last takes

place especially when the lungs are obstructed; then in fact the blood

flows back to the right cavities of the heart, then into the great

corresponding venous trunks; these are then almost equal in capacity

to the divisions they furnish, sometimes they even surpass them. 2d.

When in the living subject, a limb has been situated for a long time

perpendicularly, when standing has been long continued, for example,

then the branches are more dilated than the trunks. Now as these causes

of dilatation vary ad infinitum, the dilatations themselves are very

variable.