10 



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 3-5 



Small mononuclear 



or lymphocytes 20-25 



Eosinophil 2-4 



Mast or basophil 0*5 ,, 



