BACTERIOLOGICAL DIAGNOSIS. 



scarcely necessary to say that they should not be 

 counted. 



6. The calculation. The best way of calculating the 

 number of corpuscles present from the data thus 

 obtained is the following : 



First add up the number of corpuscles in all the 

 squares which you have counted and divide the sum by 

 the number of squares counted. This gives the average 

 in each square. 



c b 



FIG. 24. Showing method of counting red corpuscles : a, a, a, are 

 counted in square A ; b, b, in B ; c, in C. 



Now the space enclosed between each square and the 

 cover-glass above it is T V of a millimetre deep, -^ of 

 a millimetre wide, and -^ of a millimetre long ; its 

 cubic capacity is therefore -$ X ^ X ^5- = TO\JO f 

 a cubic millimetre. Therefore the ^oW P art f a 

 cubic millimetre contains the number of corpuscles 

 which we have already found as the average. 



But the square contained diluted blood ; if the amount 



