FURNITURE, AND ITS USES. 217 



to be changed in the lungs ; 1 1 are the right 

 and left branches of this artery ; m m show the 

 great veins which bring back the blood from 

 the lungs into the left auricle ; a, the left ven- 

 tricle ; c e /, the great aorta, through which 

 blood is sent out to all parts of the body ; and 

 g h i, the branches of this artery which carry 

 blood to the neck, head and arms. The little 

 arrows point always in the direction in which 

 the blood runs. 



But I must explain to you, a little more 

 fully, the motion of the heart. The blood 

 which returns from the lungs, through m m, 

 and that which returns from all the rest of the 

 body through o p q, enters both the right and 

 left auricles at the same instant, and also in 

 the same instant flows through these auricles 

 into the two ventricles. 



I ought before now to have told you that 

 there is a strong partition between the right 

 and left sides of the heart, so that the right 

 auricle and right ventricle, with their blood 

 brought back from the veins, can have nothing 

 to do with the blood in the left auricle and left 

 ventricle. It is indeed as if there were two 

 19 



