ESTIMATION OF THE RED CORPUSCLES 245 



Example. Suppose that we have counted 100 squares, and 

 have found that they contain 1,200 corpuscles, then the 

 average per square is 12. 



Then oW cubic millimetre of diluted blood contains 12 

 corpuscles. 



O r > Tlhr of ToVo undiluted blood contains 12 corpuscles, 

 supposing" the dilution was I in 100. 



Therefore i cubic millimetre of undiluted blood contains 

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



Or by the formula 



Number of corpuscles per cubic millimetre 



1,200 



- x 4,000 x 100 = 4,800,000. 

 100 



Where the dilution is I in 100 (as is recommended, since it 

 enables the red corpuscles and the leucocytes to be counted 

 in one specimen) the calculation can be simplified still further. 

 Add up the number of corpuscles in the hundred squares 

 counted and multiply by 4,000. If you count 200 squares, 

 multiply by 2,000, and so on. 



In a normal count there are 1,250 in the hundred squares 

 counted, 250 in each "bar" of twenty squares, and 12 J in each 

 small square, with the dilution of i in 100. A knowledge of 

 these facts will enable the approximate condition of the blood 

 to be obtained at a glance. 



The beginner is strongly advised to work out the problem 

 at full length until he has become absolutely familiar with the 

 reason for all the steps. 



CLINICAL APPLICATIONS. 



As this is more tedious than the estimation of the haemo- 

 globin, and is really less important in the recognition of 

 anaemia, it may often be omitted in clinical work. When 

 possible it should be done, as it serves as a useful check on 

 the results, obtained by the estimation of haemoglobin. The 

 normal numbers in health are taken to be 5,000,000 red cor- 

 puscles per cubic millimetre in adult males, and 4,500,000 in 

 adult females. As a matter of fact, these figures are very 

 frequently exceeded. In newly born children the number 

 is about 5,250,000, and in older children about 5,000,000 in 

 both sexes. Any decided fall from these figures indicates 

 anaemia. 



