6 4 



PRACTICAL HISTOLOGY. 



of the diluted blood. Evidently then, 334 x 150 = 50, 100, the number 

 of corpuscles in one cubic millimeter. But as this diluted blood con- 

 tains only T -^j part of blood, therefore 50,100 x 100 = 5,010,000, the 

 number of coloured corpuscles in one cubic millimeter of the blood 

 drawn from the finger. 



To secure an accurate result, it is, of course, essential I. that the 

 capillary be of uniform capacity throughout its entire length; 2. that 



FIG. 43. Capillary tube with diluted blood, seen through a squared ocular 

 micrometer, X 100 diam. (After Malassez). 



the blood be thoroughly mixed with the serum ; 3. that the enumera- 

 tion be accurately performed. 



The average number of coloured corpuscles in a cubic millimeter 

 of healthy human blood is 5,000,000. The number may be as high 

 as 6,000,000, and in diseased conditions it may fall as low as 800,000 

 (Malassez, lib. cit.} 



The method for counting the white corpuscles is essentially the 

 same as the above ; but, owing to their smaller number, the mixture 

 of blood and serum should contain two instead of one per cent of 

 blood. This is readily effected as follows : Fill the pipette with 

 blood to the line I, then aspirate air until the blood enters the bulb. 

 Aspirate the same quantity of blood a second time, and then mix the 

 blood with serum as before. The average number of white corpuscles 

 in a cubic millimeter of human blood is about 9000, that is about 

 T ^ of the number of the coloured corpuscles. 



