LE1SHMANIA DONOVANI 671 



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 

 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 /A long and 3 to 4 p broad, with the 

 flagellum about 22 /A 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 to 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. Attempts to 

 cultivate the kala-azar parasite on Novy and MacNeaPs medium 

 have usually been unsuccessful. 



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 piroplasma, 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. 



The question arises, given that the Leishmania donovani is 

 the cause of kala-azar, how is infection spread '( On this we 

 have as yet no certain information. Water has been looked on 

 as the carrier of infection, but the possible relationship of the 

 organism to the trypanosomata naturally suggests the idea of an 

 insect as an intermediary, and Kogers adduced some evidence that 



