WILLIAM HARVEY 47 



ventricle in the manner already indicated, — which motion we may be 

 allowed to call circular/' 



THE CIRCULATION OF BLOOD IN ANIMALS * 



Thus far I have spoken of the passages of the blood from the 

 veins into the arteries, and of the manner in which it is transmitted 

 and distributed by the action of the heart; points to which some, 

 moved either by the authority of Galen or Columbus, or the reason- 

 ings of others, will give in their adhesion. But what remains to be 

 said upon the quantity and source of the blood which thus passes, 

 is of so novel and unheard-of character, that I not only fear injury to 

 myself from the envy of the few, but I tremble lest I have mankind 

 at large for my enemies, so much doth wont and custom, that be- 

 come as another nature, and doctrine once sown and that hath 

 struck deep root, and respect for antiquity influence all men: Still 

 the die is cast, and my trust is in my love of truth, and the candour 

 that inheres in cultivated minds. And sooth to say, when I surveyed 

 my mass of evidence, whether derived from vivisections, and my va- 

 rious reflections on them, or from the ventricles of the heart and the 

 vessels that enter into and issue from them, the symmetry and size 

 of these conduits, — for nature doing nothing in vain, would never 

 have given them so large a relative size without a purpose, — or from 

 the arrangement and intimate structure of the valves in particular, 

 and of the other parts of the heart in general, with many other 

 things besides, I frequently and seriously bethought me, and long 

 revolved in my mind, what might be the quantity of blood that was 

 transmitted, in how short a time its passage might be effected, and 

 the like; and not finding it possible that this could be supplied by 

 the juices of the ingested aliment without the veins on the one hand 

 becoming drained, and the arteries on the other getting ruptured, 

 through the excessive charge of blood, unless the blood should 

 somehow find its way from the arteries into the veins, and so return 

 to the right side of the heart ; I began to think whether there might 

 not be A Motion, As It Were, In A Circle. Now this I after- 



* From An Anatomical Disquisition on the Motion of the Heart-Blood in 

 Animals. 



