ESTIMATION OF RED CORPUSCLES. 151 



of dilution was i in 100 the amount of blood contained 

 in the space over each square was T ^o part of T oVo f 

 a cubic millimetre. 



Therefore, the number of corpuscles which has been 

 determined as being the average per square is contained 

 i n TGOO f Ttjo f a cubic millimetre of undiluted blood, 

 the dilution being taken as i in 100. 



Hence the number of corpuscles in one cubic milli- 

 metre of undiluted blood is obtained by multiplying the 

 average per square by the number which expresses the 

 dilution (in this case 100) and then by 4000. 



It may be expressed as a formula, thus : 



If n is the total number of corpuscles counted, 

 s is the number of squares counted, 

 and if the dilution is i in d. 



Then the number of corpuscles per cubic millimetre 



is ~ x d x 4000. 



Example. Suppose that we have counted 100 squares 

 and have found that they contain 1200 corpuscles. 

 Then the average per square is 12. 



Then ^QTT f a cubic millimetre of diluted blood 

 contains 12 corpuscles. 



Or, T n of fdns f undiluted blood contains 12 cor- 

 puscles, supposing the dilution was i in 100. 



Therefore, one cubic millimetre of undiluted blood 

 contains 12 x 100 x 4000 = 4,800,000 corpuscles. 



Or by the formula : 



Number of corpuscles per cubic millimetre : 



1 200 



-^^- X 4000 x 100 = 4,800,000. 



The beginner is strongly advised to work out the 

 problem at full length until he has become absolutely 

 familiar with the reasons for all the steps. 



