igo CLINICAL BACTERIOLOGY AND HEMATOLOGY 



undiluted blood is obtained by multiplying the average per square 

 by the number which expresses the dilution (in this case loo), 

 and then by 4,000. 



It may be expressed as a formula, thus : 



If H is the total number of corpuscles counted, 

 5 is the number of squares counted, 

 and if the dilution is i in d, 



then the number of corpuscles per cubic milli- 

 metre is _. X ^ X 4,000. 

 s 



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 -^j^ cubic millimetre of diluted blood contains 12 cor- 

 puscles. 



O"^) liir °^ nnro ^ndihited 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 : 



1200 o 



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 12J in each small square, with 

 the dilution of 1 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 haemoglobin, 

 and is really less important in the recognition of anaemia, it may 

 often be omitted in clinical work. When possible it should be 



