MOTION OF THE HEART AND BLOOD 



the sun gives off vapors, which, rising, are condensed 

 to fall again moistening the earth. By this means 

 things grow. So also tempests and meteors originate 

 by a circular approach and recession of the sun. 



Thus it happens in the body by the movement of 

 the blood, all parts are fed and warmed by the more 

 perfect, more spiritous, hotter, and, I might say, 

 more nutritive blood. But in these parts this blood 

 is cooled, thickened, and loses its power, so that it 

 returns to its source, the heart, the inner temple 

 of the body, to recover its virtue. 



Here it regains its natural heat and fluidity, its 

 power and vitality, and filled with spirits, is dis- 

 tributed again. All this depends on the motion and 

 beat of the heart. 



So the heart is the center of life, the sun of the 

 Microcosm, as the sun itself might be called the 

 heart of the world. The blood is moved, invigorated, 

 and kept from decaying by the power and pulse 

 of the heart. It is that intimate shrine whose func- 

 tion is the nourishing and warming of the whole 

 body, the basis and source of all life. But of these 

 matters we may speculate more appropriately in 

 considering the final causes of this motion. 



The vessels for the conduction of blood are of two 

 sorts, the vena cava type and the aortic type. These 

 are to be classified, not on the basis of structure or 

 make-up, as commonly thought with Aristotle, 

 for in many animals, as I have said, the veins do 

 not differ from the arteries in thickness of tunics, 



[71I 



