DIFFERENTIAL LEUCOCYTE COUNT 267 



substance; it is then mounted in oil or balsam.) Allow it to 

 act for a quarter of an hour or more, then examine with a 

 Va-inch lens in a white light daylight if possible. In cases 

 where the reaction is present a variable number of the poly- 

 nuclears will be found to contain granules or masses of a 

 reddish-brown or mahogany colour; sometimes there are 

 large masses, and sometimes almost the whole of the proto- 

 plasm appears brown. 



The importance of this reaction is that it usually occurs, 

 and is indeed very marked, in the cases of severe sepsis in 

 which there is no increase of the total leucocyte count (see 

 p. 270), as well as in suppuration. It occurs in other con- 

 ditions, such as pneumonia, hooping-cough, uraemia, etc. In 

 many cases a small percentage only of the cells is affected, 

 and a good search must be made. 



The fact that it occurs in so many diseases detracts some- 

 what from its value in diagnosis, but when the question is 

 simply the presence or absence of pus e.g., in appendicitis 

 a positive result will usually indicate that suppuration has 

 occurred, and vice versa. Hence it is sometimes of value 

 when the leucocyte count yields uncertain results i.e., figures 

 between 16,000 to 20,000 per cubic millimetre. 



Myelocytes. Ehrlich's myelocytes occur in small numbers 

 in many infectious diseases, especially diphtheria, and occa- 

 sionally in forms of anaemia, but they are only present in large 

 numbers in myeloid leucocythaemia. Cornil's myelocytes are 

 practically limited to the latter condition, where the two forms 

 frequently together make up 60 per cent, of all leucocytes. 



Eosinophiles. An increase of eosinophiles (eosinophilia) 

 occurs to a small extent in numerous diseases, and is of diag- 

 nostic importance in the following : 



i. In diseases due to animal parasites. Here the increase 

 may be very great, as in trichinosis, where the eosinophiles 

 usually form 40 to 80 per cent, of all leucocytes, a fact of great 

 importance, and absolutely distinguishing the disease from 

 typhoid fever, rheumatism, and other diseases which may be 

 confounded with it; rarely, however, there may be no eosino- 

 philia, so that its absence does not definitely exclude the 

 disease. In bilharzia disease there is often, though not al- 

 ways, a mild eosinophilia. There is practically always an 

 increase in ankylostomiasis. It may be moderate, or may 



