54 Motion of the Heart and Blood 



than pass through continuously. And then, as the 

 blood is incessantly flowing into the right ventricle of 

 the heart, and is continually passed out from the left, 

 as appears in like manner, and as is obvious both to 

 sense and reason, it is impossible that the blood can 

 do otherwise than pass continually from the vena cava 

 into the aorta. 



Dissection consequently shows distinctly what takes 

 place [in regard to the transit of the blood] in the 

 greater number of animals, and indeed in all, up to 

 the period of their [fcetal] maturity ; and that the same 

 thing occurs in adults is equally certain, both from 

 Galen's words, and what has already been said on the 

 subject, only that in the former the transit is effected 

 by open and obvious passages, in the latter by the 

 obscure porosities of the lungs and the minute inoscula- 

 tions of vessels. Whence it appears that, although one 

 ventricle of the heart, the left to wit, would suffice for 

 the distribution of the blood over the body, and its 

 eduction from the vena cava, as indeed is done in those 

 creatures that have no lungs, nature, nevertheless, when 

 she ordained that the same blood should also perco- 

 late the lungs, saw herself obliged to add another 

 ventricle, the right, the pulse of which should force the 

 blood from the vena cava through the lungs into the 

 cavity of the left ventricle. In this way, therefore, it 

 may be said that the right ventricle is made for the 

 sake of the lungs, and for the transmission of the blood 

 through them, not for their nutrition ; seeing it were 

 unreasonable to suppose that the lungs required any SO' 

 much more copious a supply of nutriment, and that of 

 so much purer and more spirituous a kind, as coming 

 immediately from the ventricle of the heart, than either 

 the brain with its peculiarly pure substance, or the eyes 

 with their lustrous and truly admirable structure, or the 

 flesh of the heart itself, which is more commodiously 

 nourished by the coronary artery. 



