HEART AND BLOOD. 53 



whole passing over in a short space of time, it is matter of ne- 

 cessity that the blood perform a circuit, that it return to whence 

 it set out. 



But if any one shall here object that a large quantity may 

 pass through 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 milk in the mammae for 

 a cow will give three, four, and even seven gallons and more in 

 a day, and a woman two or three pints whilst nursing a child 

 or twins, which must manifestly be derived from the food con- 

 sumed; 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 same 

 thing 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 from the calculation already made, and 

 the reasons assigned, 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 much in a general way must it emit 

 upon each pulsation, and in such quantity must the blood pass, 

 the body being healthy 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 liga- 

 ture and the heart speedily to become empty; so that, unless you 

 would deny the evidence of your senses, you must needs admit 

 the return of the blood to the heart. The same thing will also 

 plainly appear when we come to discuss our second position. 



Let us here conclude with a single example, confirming all 

 that has been said, and from which every one may obtain con- 

 viction through the testimony of his own eyes. 



If a live snake be laid open, the heart will be seen pulsating 

 quietly, distinctly, for more than an hour, moving like a worm, 

 contracting in its longitudinal dimensions, (for it is of an oblong 

 shape,) and propelling its contents ; becoming of a paler colour in 

 the systole, of a deeper tint in the diastole ; and almost all things 

 else by which I have already said that the truth I contend for 



