LVII. Counting white corpuscles. 



1. Appliances. Same as in Lesson LVI with the substitu- 

 tion of the large bore pipette. 



2. Preparation. Cut a square out of a circular piece of 

 cardboard which fits in the barrel of the microscope 

 with mechanical stage. The square should be just large 

 enough to bound the counting square of the counting 

 slide. (Fig. 40). Adjust the circular card with the square in 



FIG. 40. 



FIG. 40. Plan of cardboard 

 diaphragm for microscope tube. 

 For description see LVII-2. 



FIG. 41. 



FIG. 41. Showing the sequence of 

 the fields counted. For description 

 see LVII-3 



it in the upper part of the microscope barrel just below the 

 eyepiece. By lengthening and shortening the micro- 

 scope the square can be adjusted to the square of the 

 counting slide. 

 (2) For a diluting solution, use the following : 



Acidum acet c. c. 4 



Aqua dist c. c. 100 



265 



