IO 
To Make a Differential Count of the 
Leucocytes 
Large films are necessary, especially in malaria 
where, during the apyretic period, there is a distinct 
' diminution in the total number of the white cells. It is 
important, in making films for leucocyte counting, that 
the margins and terminal points of the film be regular, 
and so in a convenient position for examination 
(Fig. 5). The margin of the film is focussed and passed 
beneath the oil immersion lens. By passing along 
the whole of the margin of the film, the great majority 
of the leucocytes in the film are seen. In order to 
obtain accurate results, one thousand leucocytes should 
be counted, but a count of three or four hundred is 
generally sufficient for diagnostic purposes. Counts of 
a smaller number of leucocytes are valueless, as too great 
variations will occur. 
As a leucocyte is seen, it is marked under the head¬ 
ing, large mononuclear, transitional, polynuclear, 
eosinophil, lymphocyte, as the case may be. As many 
as ten to twenty or more are noted mentally before 
making each record in its column. 
Normal Leucocyte Values 
Polymorphonuclear leucocytes, 65-70 per cent. 
Large mononuclear 
and transitional 
>5 
3-5 
Small mononuclear 
or lymphocytes 
>> 
20-25 
Eosinophil 
2-4 
Mast or basophil 
0-5 
