268 THE INCOME OF ENERGY 



extended through the surrounding squares, which 

 are intersected by lines ^ mm. apart. Count the 

 number of corpuscles, square by square, in 200 

 small squares. Corpuscles touching the north 

 and south lines of each area are to be counted 

 in, those touching the east and west lines are to 

 be omitted from the count. 



Each square has an area of -^fa square milli- 

 metre. The thickness of the layer of blood, i. e. 

 the distance from the ruled disc to the cover- 

 glass, is 0.1 mm. The volume of the space above 

 each square, therefore, is %$$$ cu i c millimetre. 

 As the blood is diluted 200 times its volume, and 

 the number of squares counted is 200, the total 

 number of corpuscles in a cubic millimetre is 

 a; x 200 x 4000 



200 



x being the total number of corpuscles counted. 

 In short, to obtain the number of corpuscles in a 

 cubic millimetre, multiply by 4000 the number 

 counted in 200 squares. Clean the pipette as 

 soon as the counting is done. 



Cleaning the Pipette. Draw clean Gower's 

 solution through the pipette, then alcohol, and 

 finally ether. Dry the pipette by sucking (not 

 blowing) air through it. 1 



1 Do not use alcohol and ether in cleaning the disk. Pi- 

 pettes left dirty will be cleaned at the student's expense, or, 

 where necessary, a new one purchased. 



