COUNTING THE RED CORPUSCLES 3 



difficult to get an even distribution of them in the counting cham- 

 ber, nor too slowly or one will have to wait too long for them to 

 settle. Toisson's fluid combines these qualities perhaps the best 

 of the diluting fluids in use. It has an added advantage in that it 

 stains the leucocytes, rendering it possible to count them in the 

 same preparation with the red corpuscles. Toisson's fluid should 

 be filtered before using as fungus will grow in it producing spores 

 which may be confusing in making a leucocyte count. Hayem's 

 fluid is also a suitable diluting fluid. 



Under some conditions Toisson's fluid is not the best that may 

 be used. Jones has called attention to the counts being lower 

 with Toisson's fluid than with Haj-em's in certain cases of severe 

 anemia. He found that Toisson's fluid gave lower counts in cases 

 of pernicious anemia in man and in experimental cases of anemia 

 in rabbits produced b} r bleeding or by phenylhydrazin. It would 

 be better to use Hayem's fluid in cases of severe anemia. It is 

 not certain that the formula for Toisson's fluid is the best for the 

 several species of animals. 



Formulae: 



Toisson's Fluid 



Sodium sulphate 8 grams. 



Sodium chloride 1 gm. 



Glycerin, neutral 30 cc. 



Distilled water 160 cc. 



Methyl violet, 5B 025 gm. 



Hayem's Fluid 



Mercuric chloride 0.5 gm. 



Sodium sulphate 5 gm. 



Sodium chloride 1 gm. 



Distilled water 200 cc. 



While several methods of counting the corpuscles have been 

 used, Thoma's hematocytometer, which is a combination of the 

 older instruments of Malassez, Hayem and Gower, has come to 

 be used as the most reliable. 



The instrument consists of a counting chamber with an ac- 

 curately polished piano-parallel cover glass and a diluting and 

 mixing pipette. The counting chamber is a thick glass slide on 

 which is cemented a square plate having a circular piece cut out 

 of the center. In this circular space is fastened a small circular 



