126 ADVANCED PHYSIOLOGY 



White Blood Corpuscles. White blood corpuscles are of a 

 transparent, bluish white color and are considerably larger 

 than the red ones, although the latter are about five hundred 

 times as numerous; Fig. 10. White corpuscles are real 

 cells, since they contain a nucleus, but they are constantly 

 changing their shapes. They are active little bodies which 

 sometimes move of themselves, independently of the blood 

 flow. Any part of the white corpuscle may protrude, and the 

 entire substance of the body be allowed to flow into the pro- 

 trusion. By repeating this process indefinitely, the cor- 

 puscle moves from place to place. This method of locomo- 

 tion is called amoeboid, after the amoeba, a microscopic animal 

 which moves by the same method. 



In function, too, the white corpuscles are different from 

 the red. One of their chief uses is to perform for the body 

 duties similar to those of street cleaners in our cities. They 

 are not confined inside the blood vessels, but may pass out 

 into the tissues, where they have many functions. If any 

 irritating or injurious substance gets into the body under the 

 skin, these white corpuscles collect around it in great numbers 

 for the purpose of removing it. If the irritating substance is 

 small, the white corpuscles may be able to surround it com- 

 pletely and then carry it off to be destroyed elsewhere in the 

 body. 



Another useful function of the white corpuscles is to help 

 protect the body against invading disease germs. When 

 these tiny enemies make their entrance, the white corpuscles, 

 or leucocytes, assemble quickly to do battle with them. The 

 corpuscles attack the bacteria, and may even carry off their 

 dead bodies; Fig. 68. Many of the corpuscles, as well as 

 bacteria, are killed, however, and sometimes, indeed, the bac- 

 teria overcome the corpuscles. When this occurs, the bac- 

 teria spread through the body, and the person " comes down" 

 with the disease. When the corpuscles are victors, and 

 succeed in overcoming the bacteria before they do harm, 



