ANIMAL LIFEASSIMILATION. 395 



of the organism, which feeds on it. This is 

 done by the Circulatory System, whose chief 

 function is to divide up and to apportion what 

 it receives from digestion. Two fluid mate- 

 rials are poured into it : the newly digested 

 chyle and the old venous blood. There seems 

 a tendency to duplicate the organs in this 

 system, in contrast with single organs of the 

 Digestive System. 



Circulation starts with the lungs in which 

 aeration of the blood takes place; this gets 

 oxygen and can burn, releasing force like the 

 heat of coal. Then this fire-bearing fluid 

 (temperature normally a little less than 100 

 degrees) is pumped by the heart to every 

 part of the body through the arterial pipes. 

 Passing into and out of the capillaries quite 

 extinguished, some of it returns to its source 

 for a new oxidation through the air. 



.The blood is constituted of a watery part 

 (plasma) in which float three kinds of solids: 

 corpuscles, red and white, and the so-called 

 platelets. The white corpuscles, under the 

 name of phagocytes are now regarded as the 

 standing army of the organism, whose duty 

 it is to assail and destroy the intruding foes, 

 especially the bacteria who are always mak- 

 ing incursions. Sometimes one side and 

 sometimes the other is defeated with the cor- 

 responding result of health or disease. Also 



