ESTIMATION OF THE RED CORPUSCLES 



243 



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. 



If you exclude the spaces which are thus marked with a 



FIG. 49. SHOWING METHOD OF COUNTING RED CORPUSCLES. 



a, a, a, Are counted in square A ; b, b, in B ; c, in C. In this method each 

 corpuscle is counted once, and once only. 



double line, the whole area will be marked out into a series 

 of large squares, each consisting of 4x4=16 smaller squares 

 (Fig. 49). It is convenient to count the smaller squares in 

 these groups of sixteen. At least a hundred of the smaller 

 squares i.e., six of the large groups and four small squares 

 should be counted. 



In counting one of the smaller squares it is convenient to 

 begin with the corpuscles which are lying in the middle of 

 the square, and then to count those which are lying on the 

 lines. In dealing- with these you count those which are lying 

 on the upper and left-hand lines as being within the square, 



