USE OF THE DIGESTED FOOD 



139 



color. The liquid in which they are suspended is called 

 the plasma. 



200. 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 



compound that ^ Slgg 



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. 



