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 tissues 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 substance, 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.(10) Another 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.

1. _The foods_ represent the same classes of materials as are taken in the daily fare, _i.e._, proteids, carbohydrates, fats, and salts (