36 MOTION OF THE 



ing, which, however, I cannot introduce in this place,) still their 

 anatomy plainly shows that the blood is transferred in them from 

 the veins to the arteries in the same manner as in higher ani- 

 mals, viz., by the action of the heart; the way, in fact, is patent, 

 open, manifest ; there is no difficulty, no room for hesitating 

 about it ; for in them the matter stands precisely as it would 

 in man, were the septum of his heart perforated or removed, 

 or one ventricle made out of two; and this being the case, I 

 imagine that no one will doubt as to the way by which the 

 blood may pass from the veins into the arteries. 



But as there are actually more animals which have no lungs 

 than there are which be furnished with them, and in like man- 

 ner a greater number which have only one ventricle than there 

 are which have two, it is open to us to conclude, judging from 

 the mass or multitude of living creatures, that for the major 

 part, and generally, there is an open way by which the blood is 

 transmitted from the veins through the sinuses or cavities of 

 the heart into the arteries. 



I have, however, cogitating with myself, seen further, that 

 the same thing obtained most obviously in the embryos of those 

 animals that have lungs ; for in the foetus the four vessels be- 

 longing to the heart, viz., the vena cava, the vena arteriosa or 

 pulmonary artery, the arteria venalis or pulmonary vein, and 

 the arteria magna or aorta, are all connected otherwise than in 

 the adult ; a fact sufficiently known to every anatomist. The 

 first contact and union of the vena cava with the arteria venosa 

 or pulmonary veins, which occurs before the cava opens properly 

 into the right ventricle of the heart, or gives off the coro- 

 nary vein, a little above its escape from the liver, is by a lateral 

 anastomosis ; this is an ample foramen, of an oval form, com- 

 municating between the cava and the arteria venosa, or pulmo- 

 nary vein, so that the blood is free to flow in the greatest abun- 

 dance by that foramen from the vena cava into the arteria 

 venosa or pulmonary vein, and left auricle, and from thence 

 into the left ventricle ; and farther, in this foramen ovale, from 

 that part which regards the arteria venosa, or pulmonary vein, 

 there is a thin tough membrane, larger than the opening, ex- 

 tended like an operculum or cover ; this membrane in the adult 

 blocking up the foramen, and adhering on all sides, finally 

 closes it up, and almost obliterates every trace of it. This 



