672 LEISHMANIOSIS 



effected by taking spleen juice containing the parasite, placing it in 

 10 per cent, sodium citrate solution and keeping it at 1 7° to 24° C. 

 Under such conditions there occurs an enlargement of the 

 organism, but especially of the larger nucleus. This is followed 

 by the appearance of a pink-staining vacuole in the neighbour- 

 hood of the smaller nucleus. Along with these changes, in from 

 twenty-four to forty-eight hours the parasite becomes elongated 

 and the smaller nucleus and its vacuole move to one end ; from t 

 the vacuole there then appears to develop a red-staining flagellum, 

 which when fully formed seems to take its origin from the 

 neighbourhood of the small nucleus. The body of the parasite 

 is now from 20 to 22 /*. long and 3 to 4 p. broad, with the 

 flagellum about 22 /j. long. The whole development occupies 

 about ninety-six hours. The formation of an undulating mem- 

 brane was not observed, and, although the flagellated organism 

 moved flagellum first, like a trypanosome, it is evident that here 

 the relationship of the micronucleus is different, as this structure 

 lies anterior ta the macronucleus. In his cultures, which kept 

 alive for four weeks, Leishman made a further important 

 observation the significance of which is still unknown. In cer- 

 tain of the flagellate forms he saw chromatin granules develop 

 in the protoplasm often in couples, a larger and a smaller. 

 There then occurred a very unequal longitudinal division of the 

 protoplasm, and a hair-like undulating individual containing one 

 of the pairs of chromatin granules would be split off. " At first 

 these would be non-flagellate, but later a red-staining flagellum 

 would appear at one end ; the further development of these 

 spirillary forms could not, however, be traced. The serum of 

 many animals, e.g., man, guinea-pig, has an inhibitory effect on 

 the parasite, but success in the cultivation has attended the use 

 of Novy and MacNeal's medium made up with the serum of the 

 rabbit, sheep, or dog. 



The facts just detailed have been the basis for discussion of the 

 classification of the organism, which now usually goes by the 

 name Leishmania donovani, originally given to it by Ross. 

 According to one view, it is to be looked on as a trypanosome ; 

 and although, as we have noted, its flagellated form differs from 

 the typical trypanosoma form, it bears considerable resemblance to 

 the members of this group, and, as Leishman has pointed out, his 

 cultures may not represent the full development of the organism 

 in the trypanosoma direction. Others have looked on it as a piro- 

 plasma, but Minchin's suggestion has been accepted that in the 

 present incomplete state of knowledge it is well to place it and its 

 congeners in a provisional genus, Leishmania, of the flagellata. 



