ESTIMATION OF THE RED CORPUSCLES 



207 



far as possible apart from one another, so as to get a good 

 average. In practice it is simplest to take the top one, and all 

 the others that have a double ruling; when you have counted 

 these you will have counted five rows of twenty each at equal 

 distances from one another, which will give you a very fair 

 average. (See Fig. 43, where the bars which are to be counted 

 are shaded.) 



In counting these bars count all the corpuscles which are lying 

 on or touching the top line, as in the bar you are counting, also 

 those which are lying on or touching the extreme left-hand limit 

 of the bar. Exclude those on or touching the lower and right-hand 

 lines. The reason for this will appear subsequently. 



Fig. 44. — Showing Method of Counting Red Corpuscles. 



ix, u, a, are counted in square A ; i, 6, in B ; c, in C. In this method each 

 corpuscle is counted once, and once only. 



This is the most convenient way when you have no assistant 

 to take down numbers, since you only have to remove your eye 

 from the microscope for the purpose of recording results five 

 times in the whole process, which takes about five minutes or 

 less. It is, however, rather more accurate to take down the 

 count square by square, dictating the number to an assistant, who 

 tells you when you have counted a hundred ; you are less likely 

 to make errors in the count by this method. If you follow this 

 method in place of that given above, the following notes should 

 be taken into consideration. 



