634 LEISHMANIOSIS 



to trypanosomes will be at once apparent ; the further develop- 

 ment of these spirillary forms in Leishman's organism could not, 

 however, be traced. 



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. The fact that in some 

 centres of the disease natives who are supplied with good water 

 are less liable than those who rely on the ordinary polluted 

 native cisterns, has led to the opinion that water may be the 

 carrier of infection. On the other hand, the possible relation- 

 ship of the organism to the trypanosomata naturally suggests 

 the idea of an insect as an intermediary, and Rogers adduced 

 some evidence that the bed-bug is the extra-human host. This 

 view was elaborated by Patton, who brought forward facts to 

 show that multiple cases might occur in a house while 

 neighbouring houses were free from the disease. This observer 

 also fed the common insect parasites of man in Madras on 

 patients whose peripheral blood contained the Leishmania, and 

 found that the parasite could be observed only in the pediculus 

 capitis, and in the bug, cimex macrocephalus. In the midgut of 

 the latter, forms similar to those seen in the earlier stages of 

 cultures could be found. Patton compares the organism to an 

 allied protozoon occurring in the intestine of the common fly. 

 The rarity of the Leishmania in the peripheral blood has been 

 advanced as an argument against infection taking place by means 

 of a blood-sucking insect, but it has been pointed out that 

 invisible spirillary forms may be instruments of infection. It 

 may be said here that all attempts to communicate the disease 

 to animals have been hitherto unsuccessful. 



With regard to kala-azar as a whole, we may say that we are 

 dealing with a distinct disease fairly widespread in various sub- 



