General Anatomy, Applied to Physiology and Medicine, Vol. 1 (of 3)

by Xavier Bichat

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.