173 



The methods here given are especially useful for 

 studying the blood clinically, and can not be too warmly 

 recommended. 



COUNTING BLOOD CELLS. 



The instrument now generally used for this purpose is 

 the Thoma-Zeiss hsemacytometer. This apparatus consists of 

 two parts, pipettes by means of which the blood is diluted 

 100 times, when counting red, or 10 times when white 

 blood cells are to be counted : and a glass slide, on which 

 there is a small well of known depth, the bottom of the well 

 being divided off into small squares. The pipette used 

 when counting the red cells, consists of a capillary tube, 

 , near the middle of which there is an ampullar enlargement. 

 This is so graduated that the cubical contents of the capil- 

 lary tube is just one-hundredth part of the cubical con- 

 tents of the ampulla. The blood to be examined is 

 drawn into the capillary tube, to a line marked 1 (just be- 

 low the ampulla), the end of the pipette is then inserted 

 into the diluting fluid, and this is sucked up until the di- 

 luted blood reaches aline marked 101 (just above the am- 

 pulla). The pipette is then carefully shaken to mix 

 thoroughly the blood and the diluting fluid. 



Either of the following two solutions may be used for 

 diluting the blood : 



Hayem's Solution. 



Bichloride of mercury, ... 0.5 grm. 

 Sodium chloride, . . . . 1.0 grm. 

 Sodium sulphate, .... 5.0 grms. 



Distilled water .-*-- . . . 200.0 c. c. 



Toison's Fluid (as given by Kahlden). 



Methyl violet 5 B, . .....' . 0.025 grms. 



Neutral glycerine, . . . . 30.0 c. c. 



Distilled water, .... 80.0 c. c. 



Mix methyl violet in glycerine and the distilled water; 

 to this solution is added 



Sodium chloride (C. P.), . . 1.0 grms. 



Sodium sulphate (C. P.), . . 8.0 grms. 



Distilled water, . . . 80.0 c. c. 



