Part 26

The cellular texture forms the first membrane of the arteries, and gives as we have seen insertions to the arterial fibres, but it does not extend into the interstices of these fibres; it is this that distinguishes essentially the layers of the arterial texture, from those of the muscular, venous textures, &c. I have never been able to discover the cellular texture there by any means that I could employ. Maceration, of which Haller has said so much, does not show any thing like it. When at the end of a very long time, the arteries finally yield to it, they exhibit only a kind of pulp, in which there is no cellular appearance.

In general, the resolution of the organs into cellular texture by maceration, exhibits a phenomenon much less extensive than is generally thought. It is the organic texture itself that forms the kind of pulp that is then obtained. As this texture varies in each system, the pulp of these systems, a long time macerated, varies equally; this undoubtedly would not happen, if, as Haller has advanced, the cellular texture was the only base, to which all the organs are brought by maceration. But let us return to the arteries.

Not only their fibres are not formed of cellular texture; but as I have said, they do not contain it in their interstices, a character in which it differs from all the other systems. The most careful dissection does not show it. When we separate the fibres from each other, we see, either that they are merely in apposition, or that they are held by little elongations of the same nature as themselves. I have said that this absence of the cellular texture is observable between the proper and common membranes of the arteries, though Haller has pretended the contrary.

I believe that this absence of cellular texture contributes much to the kind of brittleness that particularly distinguishes the arterial texture, and which, as I have observed, renders it the least fit of all the animal textures, to support ligatures without breaking. It is to this circumstance also that must be referred the difficulty, the impossibility even of arterial dilatations, of the formation of cysts by the parieties of arteries. There are never, we know, true aneurisms; when these tumours increase at all, the two membranes of the artery break and the cellular coat alone is dilated. Hence the necessity of the peculiar structure which distinguishes the cellular texture placed around the arteries, and gives it a resistance that it has not in most other parts. Authors are astonished at these ruptures which distinguish the dilatations of the arteries from those of all the other systems. If they had compared the texture of the arteries with that of the other systems they would have seen the reason of this difference.

We easily understand, after what has been said, why there is never fat in the arterial texture; why it is never infiltrated in dropsies; why it does not develop hydatids and cysts in its layers, why the different tumours, for which the cellular texture serves as a base, as we have seen, do not appear in the arteries, &c. When an artery has been wounded, either longitudinally or transversely, we do not see fleshy granulations arise from the edges of the wound; I do not know that surgeons have seen them in the operations for aneurisms. Never, in the numerous cases in which I have had occasion to cut the arteries, in animals, and then leave them free, after having interrupted the course of the blood, have I observed any thing like it. If an arterial trunk is laid bare, the cellular coat often furnishes these granulations; but we never see them, if this coat is removed.

_Exhalants and Absorbents._

Are there exhalants in the arteries? Nutrition undoubtedly supposes them; but it is not probable, as I have said, that they open upon their internal surface.

As to the absorbents, I thought for some time, that the absence of blood in the arteries, after death, arises from this, that their lymphatics preserving still the absorbent faculty for some time, take up the serum which is separated from the crassamentum. But lately experiments have undeceived me. I have enclosed blood, water, the fluid of dropsies, &c. between two ligatures made above and below on the common carotid, the body of which had been so managed on the exterior as not to break the vessels that come to it. At the expiration of a considerable time I have not discovered any diminution in the fluid. There had been then no absorption. I would observe that on account of the want of collateral branches, the carotid is alone proper for these experiments, and a variety of other analogous ones.

We know that the absorbents abound where there is cellular texture, and that they are wanting usually where there is none. It is probable then that the absence of this texture produces also the absence of these vessels.

_Nerves._

1st. The first tree of the system with red blood, receives almost exclusively cerebral nerves. We know in fact, that the par vagum is spread upon all the pulmonary veins, as well as upon the neighbouring vessels of the lungs, which hardly receive any from the inferior cervical ganglion. 2d. The middle portion of this system, that in which the heart is found, derives its nerves almost as much and even more, from the ganglions, than from the brain. 3d. The great tree with red blood, or the arterial, is almost exclusively embraced by the first class of nerves. We have said how these nerves go in this respect. The cerebral which accompany them, furnish hardly any filaments to the arteries. There is merely juxta position as we see it in the extremities, in the intercostal spaces, &c.

I cannot repeat it too much, that the constant relation of the arteries with the nervous system of the ganglions, deserves the attention of physiologists, because it is too general not to belong to some great object of the functions of the economy, though the object may be unknown.

ARTICLE FOURTH.

PROPERTIES OF THE VASCULAR SYSTEM WITH RED BLOOD.

What we have to say of these properties, will refer particularly to the arteries, as well as what we have said of the organization. In fact the fleshy parietes of the heart and the membranous ones of the pulmonary veins, possess properties that will be examined hereafter, and which differ from those of the arteries, on account of the difference of texture. As to those of the common membrane they are nearly the same in the whole course of the red blood, the organization differing but very little.

I shall consider the properties of the arteries only in the arterial texture and in the common membrane; for the cellular coat belonging to the system of that name, partakes of all its properties.

I. _Physical Properties._

Elasticity, which is obscure in most of the other animal textures that are characterized by a great degree of softness is very remarkable in the arteries; it is this that particularly distinguishes them from the veins. This elasticity keeps their parietes apart, though they may be empty. These tubes, with the cartilaginous, as the trachea, the meatus auditorius of the fœtus, &c. which are equally endowed with elasticity, are the only ones that keep thus open of themselves. All the others have their parietes applied to each other, when the fluid that runs through them does not distend these parietes.

It is to the elasticity of the arterial parietes that must be referred their recovering themselves when they have been flattened so as to obliterate their cavity, the sudden straightening of an arterial tube that has been bent, &c.

This property takes also an evident part in that kind of locomotion the arteries have upon the entrance of the blood. In fact, lay bare a tortuous arterial trunk in a living animal, you see the whole of it rise at each pulsation, leave the place it occupied, and straighten itself, particularly at its curves. At the moment the injection penetrates a very thin small subject, we perceive also through the integuments, a locomotion of all the tortuous branches of the face. Now it is evident that if the arteries were not of a firm and elastic texture, they would not thus obey the motion that is impressed upon them; besides, observe what takes place in the injection of the abdominal branches of the vena porta, which having no valves can be injected like arteries. Nothing similar to the locomotion of which I spoke is observed in driving the fluid into them. I have often made arterial blood circulate in the veins by the means of curved tubes, fitted to the vessels of a living animal, for example, by making the carotid and external jugular communicate; now, we observe clearly in the veins carrying the red blood, a kind of pulsation synchronous with the beating of the heart, and a distinct rustling noise, but not a real locomotion.

The locomotion of the arteries supposes three things, 1st, an agent of impulse, that communicates a motion more or less strong, to the blood contained in their interior; 2d, a tortuous arrangement which allows the blood in striking their parietes to straighten them; 3d, the firmness and elasticity of these parietes which facilitate this straightening. On the other hand, the parietes must not be too firm; thus the cartilaginous texture would be improper for this locomotion.

The elasticity of the arteries is as striking after death as during life; it is essential to distinguish it from contractility of texture. There are many distinctive characters, the following are the most striking; 1st. The contractility of texture takes place only when there is a want of extension of the arterial parietes, that is to say, when these vessels cease to contain the blood which resists their contraction, or when they are cut and afterwards left to themselves. On the contrary, elasticity requires for its exercise, a previous compression and is manifested by the sudden return of the parts to their natural state. 2d. Contractility of texture has a permanent tendency to contraction; we may say that all the parts that possess it are in a forced state; so that as soon as this state ceases, contraction takes place. On the contrary, elasticity has not this constant tendency to exercise. 3d. Every elastic motion is brisk, sudden, as quick to stop as to begin. On the contrary, every motion of contractility of texture is insensible, slow, continues often many hours and even days, as we see it in the retraction of amputated muscles, &c. 4th. Every organ in which there is contractility of texture, enjoys necessarily extensibility. On the contrary, this last property is not necessarily connected with elasticity, as we observe it in the cartilages of animals, &c. 5th. Elasticity is purely a physical property. Contractility of texture, without being vital, is only inherent in the organs of animals.

II. _Properties of texture. Extensibility._

The extensibility of the arteries may be considered, 1st, transversely; 2d, longitudinally.

The arteries have but little extensibility in the direction of their diameter. 1st. Whatever efforts are made to dilate them by injections of water, air, fat substances, &c. their caliber is rendered but little larger than natural. 2d. I have said that their texture is remarkable by a kind of brittleness, that when the blood distends them a little in aneurisms, this texture breaks instead of yielding, and that it is only the cellular coat, which, by the extensibility it has from the system from which it is derived, that is fitted to form the cyst that contains the blood. It is this that essentially distinguishes aneurismal from varicose tumours. 3d. If we tie superiorly the carotid artery of a dog, the blood pushed against the ligature that stops its course, reacts violently upon the parietes and yet the dilatation is hardly perceptible. We must not think however that the arteries do not yield at all. When the dilating cause acts slowly, it produces its effect to a certain determinate point, beyond which rupture takes place. The proof of this, is in the dilatation of the arch of the aorta, in that which true aneurisms present in their early stages, &c.

Longitudinally, the arteries are more capable of stretching, than they are transversely. We may be convinced of this, by drawing out these vessels, to place a ligature upon them in an amputated stump. By cutting upon a dead body a portion of artery, and drawing it in a contrary direction, it is evidently elongated. It is necessary in these experiments, to pay attention to the development of the folds. In fact, I have said, that this development of the folds performs a principal part in the elongation of the arteries situated in the parts that are dilated.

It is evident that in the extensibility in a transverse direction, it is the circular fibres of the peculiar membrane that especially resist; that on the contrary, in the extensibility in a longitudinal direction, it is the common membrane that opposes the resistance, since there are no longitudinal fibres. It is not astonishing then that the first kind of extensibility should be less evident than the second.

_Contractility._

It is necessary to consider it in a transverse and in a longitudinal direction.

Considered in the first point of view, contractility is much more evident than extensibility. When the artery is no longer distended with blood, it contracts in a sensible manner. It is to this contraction, that the following phenomena must be referred; 1st. the umbilical artery and the ductus arteriosus, become like ligaments after birth, by the adhesion of their parietes which are contracted. 2d. If we make a ligature upon an artery, the whole portion comprised between this ligature and the first collateral branch, soon exhibits the same phenomenon, as is proved by the operation for aneurism. 3d. If we include a portion of the carotid between two ligatures, and afterwards empty it by a puncture, it suddenly loses half its caliber. 4th. In dogs in whom I have transfused blood in order to produce artificial plethora, I have observed the arteries to be almost double in diameter, to what they are in those of the same size, who had suffered great hemorrhage. Two animals of the same size, one killed by hemorrhage the other by asphyxia, exhibit the same difference. 5th. These experiments shew me satisfactorily the cause of a large and small pulse, a cause admitted moreover by most physiologists. The artery is certainly more or less large, according to the quantity of blood that fills it. There is a point of extension that it cannot pass; but it contracts often for the want of blood, so as to be as it were, but a mere thread. 6th. Though you may have opened but few bodies, you have no doubt been astonished, that in those of the same size, the arteries have often very different diameters. This arises wholly from what takes place at the moment of death. If, from the want of blood, the arteries are for a long time contracted, they remain in this state, as happens to the heart in death by hemorrhage, &c. This is so true, that arteries of different diameters commonly become equal by injection, which brings them to an uniform degree of extension that they cannot pass. 7th. In a longitudinal wound of arteries the ends of their cut fibrous circles separating from each other, a space, which does not close, is left between them.

Most authors have confounded contractility of texture of the arteries with irritability. I have no occasion here to show how much they are deceived. In none of the preceding cases, is it necessary that a stimulant should be applied upon the arterial texture; the only thing necessary is the absence of extension, a distinctive character of the contractility of texture. Moreover it is evident, that this property continues after death, though in a less degree than during life; whereas some hours after death, every kind of irritability disappears. I think that it is especially in the arterial system, that may be seen the advantage of my division of the properties of our organs. Read all the authors upon this system, and you will see that no one is intelligible, because they have not assigned the limits of the vital properties and those of texture.

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._