2 5 8 



THE HAEMOFLAGELLATES 



flagellum has made its appearance ; when this is fully developed the 

 parasite quite resembles an ordinary Herpetomonas. 



The origin of the flagellum is interesting. A distinctive vacuole-like 

 structure arises near the end which will become the flagellar end, in close 

 connection with the kinetonucleus a point, probably, of importance. 

 This vacuole increases and suddenly is ruptured, some of its contents 

 being extruded to the exterior as a tuft or fringe of pink -staining 

 substance. In the middle of this, a small flagellum is seen, but how 

 exactly it is formed is not known. Once constituted, the flagellum grows 

 rapidly. Even in the most fully-developed Flagellate phases, however, 

 in no case has anything comparable to an undulating-membrane been 

 observed. The kinetonucleus is comparatively near one end of the body, 



VV.Bi-. 



FIG. 40. 



Stages in the development of the flagellated form. (From Leishman.) 1, ordinary spleen 

 parasite ; 2, 3, growth and vaeuolisation in cultivation ; 4, 5, appearance and growth of the 

 special " flagellar vacuole," close to the kinetonucleus ; 6, rupture of this vacuole and protrusion 

 of a tuft of pink-staining threads ; 7, growth of the flagellum, its base being inserted in the 

 collapsed vacuole ; 8, acquirement of the Herpetomonad form. 



and the flagellum springs directly from that end, not being actually 

 connected, apparently, with the former organella. 



Another remarkable process observed in these developmental forms in 

 cultures is unequal longitudinal fission. Very thin, sickle-like (" spirillar ") 

 portions of the body are split off from one side of a parent-individual. 

 More than one of these thread-like forms may be successively cut off. The 

 unusual feature of the process is that neither the two principal nuclear 

 elements nor the flagellum take part in it. Subsequently, these fission 

 forms seem to give rise to very slender flagellar ones. To what extent 

 this represents a normal (natural) mode of multiplication is uncertain. 



No other stages have been observed in cultures, and the organisms 

 degenerate and ultimately die off. The above facts demonstrated, how- 

 ever, that the Leishman-Donovan bodies can undergo important changes 

 outside the human host, and rendered it probable that they do so 

 naturally, though whether in the free condition or in an alternate host 

 was, until lately, quite unknown. The superficial position of the localised 

 form (Wright's type) points very strongly to infection by means of some 

 biting Insect, and it is natural to infer that the same holds also for the 



