CIRCULATION OF THE BLOOD 105 



with.* Finally, our position that the blood is continually 

 permeating from the right to the left ventricle, from the 

 vena cava into the aorta, through the porosities of the lungs, 

 plainly appears from this, that since the blood is incessantly 

 sent from the right ventricle into the lungs by the pulmonary 

 artery, and in like manner is incessantly drawn from the 

 lungs into the left ventricle, as appears from what precedes 

 and the position of the valves, it cannot do otherwise than 

 pass through continuously. And then, as the blood is in- 

 cessantly 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 the majority of animals, and indeed in all, up to the 

 period of their maturity; and that the same thing occurs in 

 adults is equally certain, both from Galen's words, and what 

 has already been said, only that in the former the transit 

 is effected by open and obvious passages, in the latter by 

 the hidden porosities of the lungs and the minute inos- 

 culations of vessels. It therefore 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 percolate 

 the lungs, saw herself obliged to add the right ventricle, 

 the pulse of which should force the blood from the vena 

 cava through the lungs into the cavity of the left ven- 

 tricle. In this way, it may be said, that the right ventricle 

 is made for the sake of the lungs, and for the trans- 

 mission of the blood through them, not for their nutrition; 

 for it were unreasonable to suppose that the lungs should 

 require so much more copious a supply of nutriment, and 

 that of so much purer and more spirituous a nature as 

 coming immediately from the ventricle of the heart, that 

 cither the brain, with its peculiarly pure substance, or 



' See the Commentary of the learned Hofmann upon the Sixth Book of 

 Galen. " De Usu partium." a work which I first saw after I had written 

 what precede*. 



