2 3 THE VITAL PROCESSES 



puscle to about every five hundred of the red ones. On 

 the other hand, the white corpuscles are larger than the 

 red, one of the former being equal in volume to about 

 three of the latter. 



The white corpuscles are found, when studied under 

 favorable conditions, to possess the power of changing 

 their shape and, by this means, of moving from place to 



FIG. 10. Escape of white corpuscles from a small blood vessel 

 (Hall). At A the conditions are normal, but at B some excitation in the 

 surrounding tissue leads to a migration of corpuscles. I, 2, and 3 show differ- 

 ent stages of the passage. 



place. This property enables them to penetrate the walls 

 of capillaries and to pass with the lymph in between the 

 cells of the tissues. The white corpuscles are, therefore, 

 not confined to the blood vessels, as are the red corpuscles, 

 but migrate through the intercellular spaces (Fig. 10). If 

 any part of the body becomes inflamed, the white corpus 

 cles collect there in large numbers ; and, on breaking 

 down, they form most of the white portion of the sore, 

 called the pus. 



