THE HAEMOFLAGELLATES 261 



be left unsettled. There is one point, however, which may not be 

 without significance, namely, the considerable resemblance between the 

 biology of this parasite in relation to its host (i.e. as regards mode of 

 infection, habitat, connection with the lesions, etc.) and that of Trypano- 

 soma equiperdum, the cause of Dourine or " horse-syphilis " (cf. above, 

 pp. 197, 206). 



POSTSCRIPT. 



As this article goes to press, a most interesting note by Roubaud 

 (C.R. Ac. Sci., 24th Feb. 1908, p. 423) comes to hand. This worker 

 has been investigating the relation between certain lethal Trypanosomes 

 (T. gambiense, T. brucii, T. dimorphon, and others) and Glossina palpalis, 

 and finds that the parasites undergo important changes as soon as they 

 arrive in the proboscis of the Tsetse-fly. The kinetonucleus passes to the 

 middle of the body, the undulating-membrane disappears, the flagellum 

 becomes short and thickened, and the parasites quickly attach themselves 

 to the wall of the proboscis by the flagellar end. The whole process may 

 be accomplished, indeed, in five minutes. Moreover, active multiplica- 

 tion goes on, and after a time an immense number of attached Trypano- 

 somes are present throughout the entire proboscis, often grouped in 

 masses or colonies. This " temporary culture " (culture d'attente) 

 persists for two days in the case of T. brucii, and longer up to five to six 

 days in the other forms. 



This remarkable development is apparently specific for Glossinae ; 

 it only occurs in a small number, and is doubtless due to the influence of 

 special properties of the salivary fluid. As Roubaud remarks, it prob- 

 ably affords an explanation of the selective role played by the Tsetses in 

 the propagation of different trypanosomoses in Africa. Roubaud, how- 

 ever, considers that these forms found in the proboscis are the only ones 

 capable of giving rise to an infection in a Vertebrate after the lapse of 

 twenty-four hours. This is going too far, in view of the facts now known 

 with regard to the length of time Trypanosomes may live and develop 

 in the digestive tract of Glossinae (cf. pp. 200, 230). It is noteworthy that 

 Roubaud was unable to obtain a successful inoculation from a proboscis 

 so infected. Moreover, the repeated failures of investigators to infect 

 animals from flies after forty-eight hours (cf. pp. 199, 200) seem to show 

 that the later-developed " proboscis-forms " at all events are not infective, 

 since they may reasonably be supposed to have been present in some of 

 the many experiments tried. On the other hand, there is an important 

 observation made by Bruce when working on T. brucii, to which Minchin 

 (58, p. 210) has drawn attention, showing that "wild" flies, caught 

 while feeding on a healthy animal, could infect another animal on which 

 they were subsequently fed. This certainly points to the presence of 

 some developmental phases in the Insect other than Roubaud's proboscis- 

 forms ; the proboscis had been presumably " cleaned " by the first bite 

 on the uninfected animal on which the fly was caught. And this view is 

 entirely borne out l>y Stuhlmann's recent research, summarised in the body 

 of this article. 



