474 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Enumeration of the Red Blood Corpuscles. 



The number of red blood corpuscles in blood are counted with a haemocyto- 

 meter. A drop of blood is diluted and put into a special cell, the bottom of which 

 is ruled with a number of minute squares. By microscopic observation the 

 number of corpuscles on several squares are counted. Two patterns of 

 hsemocytometer are commonly used, that of Gowers and that of Thoma-Zeiss. 



(a) With Gowers' Hcemocytometer. 



The apparatus required (Fig. 56) for enumerating the red blood corpuscles 

 consists of two pipettes A and B : A has a capacity of 995 cmm. and B of 5 cmm. ; 

 .a mixing vessel D ; a glass stirrer E ; a lancet F ; and a brass plate C for a 



FIG. 56. Gowers 1 Haemocytometer. 



microscope stage upon which is fixed a cell o'2 mm. deep. The bottom of 

 the cell is ruled with squares 'i mm. in diameter and the cell can be covered 

 with a slip which is held in place by two brass springs. 



Sodium sulphate solution of sp. gr. 1*025 is sucked up into the pipette 

 A and 995 cmm. are blown into the vessel D. 



The finger is washed with acetone and pricked with the lancet ; the first 

 drop of blood is not used but is washed away. The second drop of blood is 

 sucked up in the capillary tube B and an amount corresponding to 5 cmm. 

 is blown into the sulphate solution in D. 



The blood and sulphate are mixed with the stirrer E by rotating it between 

 the finger and thumb. A small quantily of this nrxture is placed in the cell, 

 the cell is covered and the cover slip secured in position by lifting the springs 

 upon it The corpuscles sink to the bottom of the cell upon the squares. 



The number of corpuscles on 10 squares are counted under a microscope. 

 About 50 corpuscles are the average per square. 



Their number multiplied by 10,000 gives the number in i cmm. of the 

 blood. 



