100 



Animal Microloyy 



tube and repeat the operation.) Wipe the blood from the outside of the 

 pipette and draw in sufficient Toisson's solution to make the level of the 

 combined liquids stand precisely at the mark 101. 



Toisson's solution : 



Sodium sulphate 8.0 grams 



Sodium chloride 1.0 gram 



Neutral glycerin 30.0 c.c. 



Methyl violet, 5b 0.025 gram 



Distilled water 160.0 c.c. 



"Mix the blood thoroughly with the solution by shaking the tube for 

 a few minutes. The blood is thus diluted 100 times. 



" Blow out a drop of the liquid to remove the unmixed solution remain- 

 ing in the capillary tube. Have the counting disk and cover-glass per- 



FIG. 37. Hemocytometer. 



a, view of slide from above ; b, view of slide from one side ; c, counting-disk which lies 

 at the center of B; E, bead for mixing ; M, mouthpiece. 



fectly clean. Allow a drop of the diluted blood to flow onto the disk and 

 place the cover-glass over the drop. The cell of the disk must be entirely 

 filled by the drop of blood. 



"Examine the preparation under a high power of the microscope, and 

 count the number of red corpuscles in 20 to 40 small squares; of those 

 corpuscles which happen to lie on the boundary line, count the ones that 

 lie only in the upper and on the left sides of each square. Take the 

 average number in a square and calculate the number of corpuscles in a 

 cubic millimeter of blood. 



"The depth of the entire cell is 0.1 mm., the area of each small square 

 is 4 J^ sq. mm., consequently the volume of blood in each square 

 column is 4 Vo c. mm., or 1 cubic millimeter of diluted blood would 

 contain 4,000 times the average number in a square. One cubic milli- 



