THE BLOOD 59 



New white corpuscles are formed from old ones, by cell-division. 

 Their production may occur in almost any part of the body, but usually 

 takes place in the lymphatic glands (Chapter VI) and in the spleen, 

 where conditions for their development are especially favorable. In 

 these places they are found in great abundance and in various stages of 

 development. 



Functions of White Corpuscles. The main use of the 

 white corpuscles appears to be that of a destroyer of 

 disease germs. These consist of minute organisms that 

 find their way into the body and, by living upon the tis- 

 sues and fluids and by depositing toxins (poisons) in them, 

 cause different forms of disease. Besides destroying germs 

 that may be present in the blood, the white corpuscles also 

 leave the blood and attack germs that have invaded the 

 cells. By forming a kind of wall around any foreign sub- 

 stance, such as a splinter, that has penetrated the skin, 

 they are able to prevent the spread of germs through the 

 body. In a similar manner they also prevent the germs 

 from boils, abscesses, and sore places in general from 

 getting to and infecting other parts of the body. 1 An- 

 other function ascribed to the white corpuscles is that of 

 aiding in the coagulation of the blood (page 31); and still 

 another, of aiding in the healing of wounds. 



Plasma. The plasma is a complex liquid, being made 

 up of water and of substances dissolved in the water. The 

 dissolved substances consist mainly of foods for the cells 

 and wastes from the cells. 



i. The foods represent the same classes of materials as 

 are taken in the daily fare, i.e., proteids, carbohydrates, 



1 An infected part of the body, such as a boil or abscess, should never be bruised 

 or squeezed until the time of opening. Pressure tends to break down the wall of 

 white corpuscles and to spread the infection. Pus from a sore contains germs 

 and should not, on this account, come in contact with any part of the skin. (See 

 treatment of skin wounds, Chapter XVI.) 



