MOTION OF THE HEART AND BLOOD 



the left. The lungs are relatively softer in texture 

 than the flesh and bulk of the body in the same degree 

 that the walls of the pulmonary artery differ from 

 those of the aorta. This general proportion holds 

 quite universally. The stronger, more muscular, and 

 more substantial the build of men, the thicker, 

 heavier, more powerful and fibrous the heart, and the 

 auricles and arteries are proportionally increased in 

 thickness, strength, and all other respects. 



On the other hand, in fish, birds, serpents, and 

 other such families of animals, the ventricles of the 

 heart are smooth inside, without villi or valves. The 

 walls are thinner and the arteries scarcely differ from 

 the veins in thickness of tunics. 



Further, why do the lungs have such large vessels, 

 veins as well as arteries, for the trunk of the pul- 

 monary veins exceeds both crurals and jugulars, and 

 why are they filled with so much blood? We know by 

 experience in autopsies and the advice of Aristotle, 

 not to be deceived by the appearance of such animals 

 as we encounter in dissection which have been bled 

 to death. The reason is that the source and store- 

 house of the blood, and the place for its perfecting, is 

 in the lungs and heart. 



Similarly, why do we find the pulmonary vein and 

 left ventricle in dissections so full of the same black 

 clotted blood which fills the right ventricle and pul- 

 monary artery.? Because blood continually traverses 

 the lungs from the right side of the heart to the left. 



Finally, why has the so-called vena arteriosa the 



[131I 



