236 



MANUAL OF PHYSIOLOGY. 



strong induction shocks through the blood. (4) By rapidly 

 freezing and thawing the blood several times. 



All of these processes produce the same effect, viz., the red 

 matter leaves the stroma intact. Solutions of urea, bile acids, 

 and heat of about 60 C. seem to destroy the disks, and thus re- 

 move the coloring matter. Carbolic, boracic, and tannic acids 

 cause the coloring matter to coagulate and localize itself either 

 at the centre or margin of the corpuscles (Fig. 103.) 



The number of disks in the blood of man is enormous, namely, 

 in a cubic millimetre of blood, about 5 millions for males and 4 



FIG. 104. 



Malaasez's Apparatus for the Enumeration of Blood Corpuscles. A. Measuring and mix- 

 ing pipette. B. Flattened and calibrated capillary tube. 



millions for females, or about 250,000 millions for one pound of 

 blood. The number varies much, not only in disease, but also as 

 a result of the many physiological processes, such as changes in 

 the amount of plasma, brought about by pressure differences, etc. 

 In order to count the corpuscles, the following method is em- 

 ployed : The blood is diluted with artificial plasma to 100 or 

 1000 times its volume, and the corpuscles in a portion of the mix- 

 ture carefully measured off by a capillary tube, and counted. 

 This operation requires great care and delicate apparatus. One 



