124 
TENTH REPORT. 
Counting . — The essential in counting is to set for 
one’s self definite standards, and always adhere to 
them. Only typical polymorph o-nuclear neutrophiles 
should be counted. It is also well to use the same 
portion of the smear for counting, both for the pati- 
ent’s blood and for the control, as there is liable to be 
some difference in the count between those leucocytes 
found along the edges and those found at the end of 
the smear. It is also well to have some disinterested 
party occasionally mark the slides in cipher so as to 
eliminate any psychical error in counting. 
Fig. 20. — Spreader. 
Table I. — Counting for the Opsonic Index. 
Chart showing the number of bacteria counted in a series of leucocytes and the method of finding 
the phagocytic count and the opsonic index. 
The number of bacteria (135) found in fifty leucocytes is multiplied by two to give the number in 
100, then pointing off two places, gives the average per leucocyte (2.7); the phagocytic count of the 
patient divided by the phagocytic count of the pool gives the opsonic index (1.17). 
Fig. 21. — Making the smear. 
