FURNITURE, AND ITS USES. 221 



But this is a digression, though it is a neces- 

 sary one. I will now go back and proceed to 

 describe the motion of the heart. 



We have seen how it is that the blood gets 

 out of the auricles into the ventricles, and why 

 it goes into the ventricles rather than backward 

 into the veins. Now the ventricles both con- 

 tract ; and as was the case with the two auricles, 

 they both contract in the same instant. This 

 contraction pushes their blood into the arteries, 

 as I have before told you. The right ventricle 

 pushes its blood into the pulmonary artery, 

 whence it goes to the lungs ; and the left ven- 

 tricle pushes its blood into the great aorta, 

 through which it goes to every part of the 

 body. 



Why does not the blood, when the ventricle 

 contracts, go back into the auricle ? Because 

 there are valves between them which imme- 

 diately spread out, like so many flaps or clap- 

 pers, and form a sort of partition or floor, as 

 the valves do in the veins, and prevent it. 

 They do not, it is true, prevent every drop of 

 it from returning. A very small quantity gets 

 back, but none worth mentioning. 

 19* 



