LEISHMANIA DONOVANI 407 



diameter from 2 to 5 microns and the shorter 1-5 to 2-5 microns. In these 

 forms one end is often more rounded than the other. Occasionally, more 

 elongated forms somewhat resembling a cigar or torpedo in shape occur, 

 and in these the kinetoplast may be so closely applied to the nucleus as 

 to escape recognition (Fig. 192). In the smear of a child's spleen made 

 by the writer in Malta, the majority of the parasites were of this type. 

 Occasionally, larger parasites occur, especially in inoculated animals, 

 where they may attain a diameter of 8 or 9 microns. In a spleen smear 

 from a typical case of kala azar there occur numbers of large cells, the 

 macrophages, some of which are packed with parasites. Many of these 

 cells will have broken down in preparation of the smear, and the liberated 

 parasites will be scattered amongst the debris. Detached portions of the 

 cytoplasm of these cells containing groups of leishmania have been called 

 " gangues" by French writers (Plate IV., 2, 4, 8, p. 406). In less heavily 

 infected cases a careful examination of the films will have to be made, as 



Fig. 189. — Flagellate Forms of Leishmania donovani in the Tissues of an 

 Experimentally Infected Dog ( x ca. 2,000). (After Wenyon, 1915.) 



the parasites may be present in very small numbers. A group of two 

 or three parasites, or even single ones, will be found in the cytoplasm of 

 a small percentage of the cells. In such cases, careful attention must be 

 paid to the morphology, and no structure should be called a leishmania 

 unless the sharp outline, the deeply staining rod-like kinetoplast and 

 the more palely staining and larger nucleus have been clearly seen. The 

 crucial test in any doubtful case is the development of the flagellate lepto- 

 mouas form in culture. In every film, in addition to the parasites which 

 show the typical structure, there occur abnormal or degenerate types, 

 about the nature of which it is often impossible to form an opinion. 



As seen in dried smears stained by the usual Romanowsky methods, 

 the nucleus appears as an aggregation of red-staining granules. This is 

 an artificial picture, for in films which have been fixed, without drying, 

 in a suitable fixative, and stained by the iron-haematoxylin method, the 

 nucleus is seen to have a membrane enclosing a clear space, at the centre 



