4 6 



Motion of the 



witness of their reality. "The pulse," he observes, 

 *' inheres in the very constitution of the heart, and 

 .appears from the beginning, as is learned both from 

 the dissection of living animals, and the formation of the 

 chick in the egg." * But we further observe, that 

 the passages in question are not only pervious up to 

 ithe period of birth in man, as well as in other animals, 

 as anatomists in general have described them, but for 

 several .months subsequently, in some indeed for several 

 years, not to say for the whole course of life ; as, for 

 example, in the goose, snipe, and various birds, and 

 many of the smaller animals. And this circumstance 

 it was, perhaps, that imposed upon Botallus, who 

 thought he had discovered a new passage for the 

 blood from ,the vena cava into the left ventricle of 

 the heart ; and I own that when I met with the same 

 .arrangement in one of the larger members of the 

 mouse family, in the adult state, I was myself at first 

 led to something of a like conclusion. 



From this it will be understood that in the human 

 embryo, and in the embryos of animals in which the 

 communications are not closed, the same thing happens, 

 ;namely, that the heart by its motion propels the blood 

 by obvious and open passages from the vena cava into 

 the aorta through the cavities of both the ventricles ; 

 the right one receiving the blood from the auricle, and 

 ipropelling it by the vena arteriosa, or pulmonary artery, 

 and its continuation, named the ductus arteriosus, into 

 the aorta ; the left, in like manner, charged by the 

 contraction of its auricle, which has received its supply 

 through the foramen ovale from the vena cava, con- 

 tracting, and projecting the blood through the root of 

 the aorta into the trunk of that vessel. 



In embryos, consequently, whilst the lungs are yet in 

 a state of inaction, performing no function, subject to 

 isno motion any more than if they had not been present, 

 mature uses the two ventricles of the heart as if they 



1 Lib. de Spiritu, cap. v 



