74 HANDBOOK OF PHYSIOLOGY. 



can be reproduced five or six times in succession. If, however, the ac- 

 tion of the carbonic acid be much prolonged, the granulation of the 

 nucleus becomes permanent; it appears to depend on a coagulation of 

 the paraglobulin. 



Heat. The effect of heat up to 120-140 F. (50-60 0.) is to 

 cause the formation of a number of bud-like processes (Fig. 73). 



Electricity causes the red blood-corpuscles to become crenated, and 

 at length mulberry-like. Finally they recover their round form and 

 become quite pale. 



The Colorless Corpuscles. In human blood the white or colorless 

 corpuscles or leucocytes are nearly spherical masses of granular proto- 

 plasm without cell. wall. The granular appearance more marked in 

 some than in others (vide infra), is due to the presence of particles 

 probably of a fatty nature. In all cases one or more nuclei exist in each 

 corpuscle. The size of the corpuscle averages -y-^ of an inch in 

 diameter. 



In health, the proportion of red to white corpuscles, which, taking an 



FIG. 74. A. Three colored blood-corpuscles. B. Three colorless blood-corpuscles acted on by 

 acetic acid ; the nuclei are veiy clearly visible, x 900. 



average, is about 1 to 500 or 600, varies considerably even in the course 

 of the same day. The variations appear to depend chiefly on the 

 amount and probably also on the kind of food taken; the number of 

 leucocytes being very considerably increased by a meal, and diminished 

 again on fasting. Also in }*oung persons, during pregnancy, and after 

 great loss of blood, there is a larger proportion of colorless blood-corpus- 

 cles, which probably shows that they are more rapidly formed under 

 these circumstances. In old age, on the other hand, their proportion is 

 diminished. 



Varieties. The colorless corpuscles present greater diversities of 

 form than the red ones. Two chief varieties are to be seen in human 

 blood; one which contains a considerable number of granules, and the 

 other which is paler and less granular. In size the variations are great, 

 for in most specimens of blood it is possible to make out, in addition to 

 the full-sized varieties, a number of smaller corpuscles, consisting of a 

 large spherical nucleus surrounded by a variable amount of more or less 

 granular protoplasm. The small corpuscles are, in all probability, the 

 undeveloped forms of the others, and are derived from the cells of the 

 lymph. 



Besides the above-mentioned varieties, Schmidt describes another 



