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MANUAL OF PHYSIOLOGY. 



4i 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 



FJG. 105. 



The appearance presented by the Capillary Tube of Malassez's Apparatus 

 when filled with diluted blood and examined under a microscope magnify- 

 ing 100 diameters provided with an eye-piece micrometer. 



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 

 of the best-known methods is that of Malassez, the details of 

 which are as follows : 



Blood is drawn into the capillary tube of a specially prepared 

 delicate pipette (Fig. 104, A) up to a mark which indicates 



