252 TEXT-BOOK OF PHYSIOLOGY. 



containing a proteid resembling cell-globulin, lecithin, cholesterin, and 

 inorganic salts, among which potassium phosphate is especially abundant. 



HISTOLOGY OF THE WHITE CORPUSCLES OR LEUKOCYTES. 



The presence of white corpuscles in the blood can be readily observed 

 under the same conditions as the red corpuscles are observed. Thus when 

 the mesentery of the frog or the guinea-pig is examined with the microscope 

 the white corpuscles are seen adhering to the walls of the blood-vessels; in 

 a drop of freshly drawn blood they are found in the spaces between red 

 corpuscles (Fig. 97.) A careful examination of the blood by the employ- 

 ment of appropriate methods has revealed the presence of several varieties of 

 white corpuscles, to which reference will be made in a subsequent paragraph. 



Shape and Size. In the resting condition, whether seen in the vessel 

 or on the stage of the microscope, the white corpuscle, as its name implies, is 

 grayish in color, round or globular in form, though often presenting a more 

 or less irregular surface. Its diameter varies from 0.004 to 0.013 mm., 

 though the average is about o.on mm. or about -grVo- mc ^' 



Structure. A typical white corpuscle consists of a ground-substance 

 uniformly transparent and apparently homogeneous, in which are embedded 

 a number of granules of varying size, some of which are very fine, while 

 others are large. By various reagents it has been demonstrated that the 

 granules are fatty, protein, and carbohydrate (glycogen) in character. In 

 the fresh cells the existence of a nucleus is difficult of detection, though its 

 presence can be demonstrated by the addition of acetic acid, which renders 

 the perinuclear cytoplasm more transparent and makes the nucleus con- 

 spicuous and sharply defined. From its structure it is apparent that the 

 white corpuscle belongs to the group of undifferentiated tissues and resembles 

 the cells of the embryo in its earliest stages as well as the unicellular organism, 

 the amoeba. 



Chemic Composition. The chemic composition of the white corpuscles 

 has been inferred from an analysis of pus-corpuscles, with which they are 

 practically identical, and of lymph-corpuscles from the lymph-glands. Of 

 the corpuscle about 90 per cent, is water and the remainder solid matter 

 consisting mainly of proteins, of which nuclein, nucleo-albumin, and cell 

 globulin are the most abundant. The two former are characterized by the 

 presence of a considerable quantity of phosphorus, amounting to as much as 

 10 per cent. Lecithin, fat, glycogen,. and earthy and alkaline phosphates 

 are also present. 



Number of White Corpuscles. The number of white corpuscles per 

 cubic millimeter of blood is much less than the number of red corpuscles, the 

 ratio being in the neighborhood of i white to 700 red. This ratio, however, 

 varies within wide limits in different portions of the body and under normal 

 variations in physiologic conditions. In the blood of the splenic artery there 

 is but i white to 2260 red, while in the splenic vein there is i white to every 

 60 red; or about thirty-eight times as many as in the artery. In the portal 

 vein there is i white to 740 red, while in the hepatic vein there is i white to 

 170 red. 



The total number of white corpuscles per cubic millimeter has been 



