THE CIRCULATORY OR VASCULAR SYSTEM 135 



the lymph-spaces. In inflammations the cells pass out in 

 great numbers, and in suppurative conditions they become 

 pus cells. 



The white cells migrate to the part infected, surround 

 the substances, and, through their protective powers, 

 prevent further intoxication of the system. This sur- 

 rounding and absorption of infective matter is termed 

 phagocytosis, and the white corpuscles, when acting in 

 this manner, are spoken of as phagocytes. 



This phagocytic action is aided by a certain chemic 

 substance, called opsonin, which exists in the blood-plasma, 



FlG. 67. Various forms of leukocytes : a, Small lymphocyte ; b, large 

 lymphocyte; c, polymorphonuclear neutrophile ; d, eosinophile (Leroy). 



and whose function is to act on disease germs, so as to 

 prepare them for absorption by the white cells. 



The blood-plates are small colorless or yellowish bodies 

 of varying shape, but considerably smaller than the red 

 corpuscles. It is still uncertain whether these bodies 

 are independent structures or only fragments of destroyed 

 red corpuscles. 



The plasma of the blood is a white, yellowish, clear 

 fluid, largely composed of water, holding in solution vari- 

 ous salts, proteid substances, fats, etc. The proteid 

 materials are made up of albumin, paraglobulin, and 

 fibrinogen; the first two occur in about equal quantities, 

 while the last is found in small quantities. 



Nutrition is gained through the albuminoids, which 

 replenish the tissues of waste materials taken up through 

 the processes of combustion and disease. 



