VSB OF THE DIGESTED FOOD 



139 



color. The liquid in which they are suspended is called 

 the plasma. 



^00. The blood corpuscles (Fig. 6). — ^The corpuscles 

 are not mere masses of unformed matter, but they are 

 minute bodies having a definite form and structure. They 

 make up from 35 to 40 per cent of the blood, and con- 

 tain over 30 per 



cent of dry 

 matter. This 

 dry matter con- 

 sists mostly of 

 hemoglobin, a 

 compoimd that 

 is peculiar to the 

 blood and equips 

 it for one of its 

 most important 

 offices. Hemo- 

 globin, when 

 broken up in the 

 absence of oxy- 

 gen, is found to 

 be made up of a 

 protein (globin- 

 histone) and a 

 coloring matter 

 (hemochromogen) in the latter of which is combined a 

 definite proportion of iron. When broken up in the pres- 

 ence of oxygen we get globin and hematin, as hemo- 

 chromogen when oxydized becomes hematin. The peculiar 

 property of hemoglobin which renders it so useful a con- 

 stituent of the blood is its power of taking up oxygen 

 and holding it in a loose combination until it is needed 



Fig. 6. Red and white corpuscles of blood 

 (magnified). A, red corpuscles; a, a, white cor- 

 puscles; B, C, D, red corpuscles, more highly 

 magnified; F, G, white corpuscles, more mag- 

 nified. 



