THE CIRCULATORY OR VASCULAR SYSTEM 133 



The relative proportion of the white to the red cor- 

 puscles has been variously estimated by many observers, 

 and varies from i to 400 to i to 1200. 



The red corpuscles (erythrocytes) are round biconcave 

 discs; their average diameter is estimated to be about 

 j^nr f an mcn - They vary in size when disease, such as 

 anemia, exists. 



Composition. The composition of the red cell is esti- 

 mated to be as follows : 



Water 90.0 per cent. 



Hemoglobin 36.0 " 



Proteids 3.2 " 



Lecithin and cholesterin 0.2 " 



Inorganic salts 0.6 " 



Their color is due to the hemoglobin which they contain ; 

 by some the color is said to be due to iron. The function 

 of the red corpuscles is to carry oxygen (through the in- 

 tervention of the hemoglobin they contain); therefore, 

 they are denominated "oxygen carriers." The blood 



FlG. 66. Cells of blood: a, Colored blood-corpuscles seen on the flat; 

 6, on edge ; c, in rouleau ; d, blood-platelets (Leroy). 



passing to the lungs receives a new supply of oxygen, and 

 returns to the tissues, where combustion takes place, 

 which deposits the oxygen, whereby heat and energy are 

 produced ; it now takes on new substances (carbon dioxid) 



