552 FAMILY: TRYPANOSOMID^ 



infection in the dog. From what has been stated above, it is evident 

 that there are no means of distinguishing the trypanosomes which occur 

 naturally in game and tsetse flies from the form found in man. Kleine 

 (1923), who regards the human strain as a species {T. rhodesiense) dis- 

 tinct from T. brucei, maintains that, in spite of morphological identity, 

 the forms seen in the wild animals by Bruce and his co-workers and by 

 Kinghorn and Yorke are T. brucei, and that a true reservoir for the human 

 trypanosome, T. rhodesiense, has yet to be discovered, 



{b) Trypanosomes which Develop in the Stomach and Proboscis of Tsetse 

 Flies — Monomorphic Trypanosomes without Flagella. 



Trypanosoma congolense Broden, 1904. — Synonyms: T.dimor'plion'LsiVGxan 

 and MesnU, \W4: pro x>arte ; T. wfwmm Laveran, 1905; Trypanozoon dimorphon {Liihe, 

 1906) 2rro 2)(irte ; T. nanum (Liihe, 1906); T. congolense (Liilie, 1906); Trypanosoma 

 confusum Montgomery and Kinghorn, 1909; T. pecortim Bruce et al., 1910; T. soma- 

 liense Martoglio, 1911; T. cellii Martoglio, 1911; T. frobeniusi Weissenborn, 1911; 

 Duttonella pecorum (Chalmers, 1918); T. montgomeryi Laveran, 1909 (?); T. ruandce 

 van Saceghem, 1921. 



Distribution. — This is a small trypanosome found chiefly in cattle, 

 but also in horses and sheep. It was first recorded by Broden (1904) in 

 the Congo. What was probably the same form was discovered by Balfour 

 and Head in the Sudan, and was named T. nanum by Laveran (1905f/). 

 Montgomery and Kinghorn (1909) suggested the name T. confusum for 

 this trypanosome on account of the doubt as to its identity. Finally, 

 Bruce et al. (19106), because of the same confusion, proposed to start 

 de novo with the name T. pecormn. There seems little doubt that all these 

 forms are identical, in spite of certain differences as regards the suscepti- 

 bility of small laboratory animals. T. nanum, for instance, as noted by 

 Bruce et al. (19116), is said to be not inoculable into rats and mice, whereas 

 the form named T. jpecorum could be often transmitted to these animals. 

 Bruce (1914), however, stated that after passage through the goat, 

 T. pecorum ceased to infect rats and mice, and came to the conclusion that 

 T. nanmn was merely a strain of T. pecorum which had lost its virulence. 

 Aders (1923) in Zanzibar has noted the same loss of virulence after passage 

 through the goat, sheep, and giant rat. Morphologically, the various 

 forms are indistinguishable, and it seems safer to regard the small patho- 

 genic trypanosomes which are widely distributed in Africa as belonging to 

 one species. There is a greater difficulty, however, with a form which 

 was named T. dimorphon by Laveran and Mesnil (1904). This trypano- 

 some was first seen by Button and Todd in the Gambia in 1903, and the 

 strain brought home was sent to Laveran and Mesnil, who have employed 

 it in a long series of investigations. They maintain (1912) that it is 

 distinct from any of the forms mentioned above, not onlv because of cross- 



