DIFFERENTIAL LEUCOCYTE COUNT 32g 



second person, who takes them down as described ; you do not 

 then have to look constantly from the microscope to the paper 

 and vice versa, and the whole process takes a very few minutes 

 unless the leucocytes are very scanty. 



For most clinical purposes 400 leucocytes will be enough to 

 count, though where very great accuracy is required 1,000 is 

 not too many. Having counted the required number, proceed 

 to count the numbers of P's, L's, etc., and reduce them to a 

 percentage. 



Whilst making the differential count keep a sharp look-out for 

 abnormal leucocytes, abnormal red corpuscles (see p. 233), 

 parasites, etc. The collections of blood platelets which form 

 such a prominent feature in some blood films should not be 

 confounded with anything else, as they are quite characteristic, 

 though a single blood platelet lying on the top of a red corpuscle 

 may look very like a young malaria parasite. Each platelet is a 

 very small mass which stains blue or purple with Jenner's stain, 

 and often appears hollow or irregular in shape, and they are often 

 grouped in masses of quite large size. 



Alterations in Disease. 



Lymphocytes. — They may be relatively increased [e.g., to figures 

 above 30 per cent.) when the total figures are normal or raised. 

 These findings have different meanings. 



Lymphocytosis with normal or lowered total counts occurs in 

 pernicious ansmia, typhoid fever, uncomplicated tuberculosis 

 (but not always), in some cases of purpura (so-called idiopathic 

 purpura), in splenic anaemia, and occasionally in syphilis, 

 Hodgkin's disease, and some other diseases. 



Lymphocytosis with a high total count occurs as a normal 

 condition in infancy, and is accentuated both as regards the 

 percentage of lymphocytes and the total number of leucocytes in 

 almost all infantile diseases, especially rickets and hooping-cough. 



In adults a very high total count (100,000 or more) with a very 

 high percentage of lymphocytes (up to 99-5 per cent.) indicates 

 lymphatic leucocythaemia. Smaller increases sometimes occur 

 in other diseases. 



A relative diminution of the lymphocytes frequently occurs as a 

 result of the increase of other leucocytes, rarely as a true absolute 

 diminution. 



