KALA-AZAR l6l 



is considerably increased. It is only in the early stages 

 that kala-azar is likely to be mistaken for enteric fever, 

 from which the points just mentioned should serve to 

 distinguish it. 



The examination of the blood is an essential preliminary 

 step in the diagnosis of kala-azar. The combination of 

 marked leucopenia with relative increase in the number 

 of mononuclear leucocytes at once differentiates it from 

 a number of diseases which at some stage or other 

 resemble it in some respects, but in which this condition is 

 absent. Such are enteric fever and undulant fever among 

 acute diseases, and splenic anaemia (Banti's disease) and 

 spleno-medullary leucocythemia among chronic diseases, 

 in all of which the spleen may be considerably enlarged, 

 and a varying degree of anaemia present, but in which 

 the number of leucocytes is increased in the chronic 

 anaemias very greatly so. In patients suffering from 

 tropical abscess of the liver there is usually leucocytosis. 

 This may not be marked in some cases, but there is no 

 leucopenia. A blood count would differentiate the two 

 diseases, the total number of leucocytes being in excess in 

 hepatic abscess and diminished in kala-azar. 



The diseases other than kala-azar in which leucopenia 

 is combined with a relative mononuclear increase are 

 malaria and trypanosomiasis. In malaria, however, leuco- 

 penia is less marked than in kala-azar, the relative pro- 

 portion of white and red corpuscles remaining the same 

 as in normal blood, about i to 750. In kala-azar, on the 

 contrary, the diminution of white corpuscles is much 

 greater than that of the red, the proportion falling as low 

 as i to 1,500, or even as i to 3,000. 



In ankylostomiasis there is leucocytosis at the onset of 

 the disease with marked eosinophilia. 



Examination of the blood alone should not, however, 

 unless the specific parasites of these diseases are recog- 

 nized, be relied upon to differentiate them from kala-azar. 



To place the diagnosis beyond doubt the demonstration 

 of the parasite of kala-azar is necessary. The parasite is 

 ii 



