Part 8 (1/2)

This truth, indeed, presents itself obviously before us e consider what happens in the dissection of living anireat artery need not be divided, but a very sard to man), to have the whole of the blood in the body, as well that of the veins as of the arteries, drained away in the course of no long time--some half-hour or less Butchers are well aware of the fact and can bear witness to it; for, cutting the throat of an ox and so dividing the vessels of the neck, in less than a quarter of an hour they have all the vessels bloodless--the wholealso occasionally occurs with great rapidity in perfor tuu ani amputations, the blood escaped in equal, if not perchance in larger quantity by the veins than by the arteries The contrary of this statement, indeed, is certainly the truth; the veins, in fact, collapsing, and being without any propelling power, and further, because of the impediment of the valves, as I shall show immediately, pour out but very little blood; whilst the arteries spout it forth with force abundantly, ie And then the experi the vein untouched and only dividing the artery in the neck of a sheep or dog, when it will be seen hat force, in what abundance, and how quickly, the whole blood in the body, of the veins as well as of the arteries, is emptied But the arteries receive blood froh the heart, as we have already seen; so that if the aorta be tied at the base of the heart, and the carotid or any other artery be opened, no one will now be surprised to find it empty, and the veins only replete with blood

And now the cause is e a quantity of blood in the veins, so little in the arteries; why there is ht ventricle, little in the left, which probably led the ancients to believe that the arteries (as their na the life of an animal The true cause of the difference is perhaps this, that as there is no passage to the arteries, save through the lungs and heart, when an anis to move, the blood in the pul into the pulmonary veins, and from thence into the left ventricle of the heart; just as we have already seen the same transit prevented in the es and the alternate opening, and shutting of their hidden and invisible porosities and apertures But the heart not ceasing to act at the sa the to pulsate for a ti their blood to the body at large and sending it into the veins; receiving none fros, however, they are soon exhausted, and left, as it were, ethat it can be ascribed to no other than the cause we have just assumed

Moreover, it appears from this that the more frequently or forcibly the arteries pulsate, thehe fits and in states of alaruidly and less forcibly, hees are diminished and arrested

Still further, it is from this, that after death, when the heart has ceased to beat, it is iular or femoral veins and arteries, by any effort, to force out more than one-half of the whole mass of the blood Neither could the butchers ever bleed the carcass effectually did he neglect to cut the throat of the ox which he has knocked on the head and stunned, before the heart had ceased beating

Finally, we are now in a condition to suspect wherefore it is that no one has yet said anything to the purpose upon the anastomosis of the veins and arteries, either as to where or how it is effected, or for what purpose I now enter upon the investigation of the subject

CHAPTER X

THE FIRST POSITION: OF THE QUANtitY OF BLOOD PassING FROM THE VEINS TO THE ARTERIES AND THAT THERE IS A CIRCUIT OF THE BLOOD, FREED FROM OBJECTIONS, AND FARTHER CONFIRMED BY EXPERIMENT

So far our first position is confir be referred to calculation or to experiment and dissection, viz, that the blood is incessantly poured into the arteries in larger quantities than it can be supplied by the food; so that the whole passing over in a short space of time, it is matter of necessity that the blood perform a circuit, that it return to whence it set out

But if anyone shall here object that a large quantity h and yet no necessity be found for a circulation, that all may come from the meat and drink consumed, and quote as an illustration the abundant supply of ive three, four, and even seven gallons anda child or twins, which must manifestly be derived from the food consumed; it may be answered that the heart by computation does as much and more in the course of an hour or two

And if not yet convinced, he shall still insist that when an artery is divided, a preternatural route is, as it were, opened, and that so the blood escapes in torrents, but that the sa does not happen in the healthy and uninjured body when no outlet is made; and that in arteries filled, or in their natural state, so large a quantity of blood cannot pass in so short a space of time as to make any return necessary--to all this it may be answered that, froned, it appears that by so much as the heart in its dilated state contains, in addition to its contents in the state of constriction, so eneral way must it emit upon each pulsation, and in such quantityentire and naturally constituted

But in serpents, and several fishes, by tying the veins some way below the heart you will perceive a space between the ligature and the heart speedily to become empty; so that, unless you would deny the evidence of your senses, you must needs ad will also plainly appear e come to discuss our second position

Let us here conclude with a single exa all that has been said, and froh the testimony of his own eyes

If a live snake be laid open, the heart will be seen pulsating quietly, distinctly, for itudinal di its contents It becomes of a paler colour in the systole, of a deeper tint in the diastole; and als else are seen by which I have already said that the truth I contend for is established, only that here everything takes place more slowly, and is more distinct This point in particular may be observed more clearly than the noonday sun: the vena cava enters the heart at its lower part, the artery quits it at the superior part; the vein being now seized either with forceps or between the finger and the thumb, and the course of the blood for some space below the heart interrupted, you will perceive the part that intervenes between the fingers and the heart al exhausted by the action of the heart; at the same time the heart will become of a much paler colour, even in its state of dilatation, than it was before; it is also sins to beat th as if it were about to die But the i removed, instantly the colour and the size of the heart are restored

If, on the contrary, the artery instead of the vein be compressed or tied, you will observe the part between the obstacle and the heart, and the heart itself, to become inordinately distended, to assuth to be so much oppressed with blood that you will believe it about to be choked; but the obstacle res immediately return to their natural state and colour, size, and impulse

Here then we have evidence of two kinds of death: extinction from deficiency, and suffocation from excess Examples of both have now been set before you, and you have had opportunity of viewing the truth contended for with your own eyes in the heart

CHAPTER XI

THE SECOND POSITION IS DEMONSTRATED

That this may the more clearly appear to everyone, I have here to cite certain experiments, from which it seems obvious that the blood enters a limb by the arteries, and returns fro the blood fro channels of the blood to the heart; that in the limbs and extreme parts of the body the blood passes either immediately by anastomosis from the arteries into the veins, or mediately by the porosities of the flesh, or in both ways, as has already been said in speaking of the passage of the blood through the lungs whence it appears manifest that in the circuit the blood moves from that place to this place, and from that point to this one; from the centre to the extremities, to wit; and frorounds of calculation, with the same elements as before, it will be obvious that the quantity can neither be accounted for by the ingeata, nor yet be held necessary to nutrition

The saatures, and wherefore they are said to draw; though this is neither from the heat, nor the pain, nor the vacuuht of; it will also explain the uses and advantages to be derived froatures in medicine, the principle upon which they either suppress or occasion he and more extensive mortification in extremities; and how they act in the castration of animals and the removal of warts and fleshy tuhed and understood the cause and rationale of these various effects, that though alatures in the treatment of disease, yet very few comprehend their proper employ cures