TRYPANOSOMA VIVAX 561 



sometimes be inoculated and the strain carried on in them. Kleine (1923) 

 states that on one occasion he produced a transitory infection in a monkey. 

 Morphology. — T. vivax can be distinguished from other pathogenic 

 trypanosomes, not only by its activity, which enables it to dash about in 

 a fresh blood preparation with great energy, but also by its morphological 

 features (Fig. 232, B, and Plate V., f, p. 456). It measures 18 to 26 microns 

 and has a definite flagellum. As regards the structure of the body, 

 the bulk of the cytoplasm lies posterior to the nucleus, giving to this 

 part of the body, which consists of a clear alveolar cytoplasm, a swollen 

 and broad appearance. The body narrows at the nucleus and tapers ofE 

 to the anterior end. The kinetoplast is at or near the posterior extremity, 

 and is well developed. The nucleus is central, while the undulating 

 membrane is less developed and the axoneme straighter than in T. brucei 

 or T. evansi. The flagellum is 3 to 6 microns in length. 



Transmission and Reservoir. — T. vivax was found in the blood of a 

 bush buck by Bruce et al. (1910e) in Uganda. Rodhain, Pons, Vanden- 

 branden, and Bequaert (1912) recovered the trypanosomes from various 

 antelopes in the Belgian Congo, as also did Kinghorn and Yorke (1912a) 

 in North-East Rhodesia (see p. 508). 



Several species of tsetse fly are capable of transmitting T. vivax. 

 Bruce et al. (1910a, 1911 A) found that development took place in about 

 20 per cent, of Glossina palpalis fed on infected animals. These flies were 

 also found naturally infected. The researches of Pecaud (1909), Bouffard 

 (1909, 1910), Bouet and Roubaud (1910, 1911a), and Roubaud (1910) 

 have shown that the trypanosome with which they worked, and which 

 they called T. cazalhoui, could be transmitted by G. palpalis, G. tachi- 

 noides, G. longipalpis, and by G. morsitans, while Rodhain, Pons, Vanden- 

 branden, and Bequeert (1912) also transmitted it by G. morsitans. 



Cycle in the Fly. — The development in the fly as first noted by Bruce 

 et al. (1910a) illustrates a third type of evolution (Fig. 219). In this case 

 there is no stomach phase of development, the multiplication of the try- 

 panosomes taking place in the proboscis only. Crithidia forms are pro- 

 duced in the labial cavity, and these attach themselves in large numbers 

 to its walls. The hypopharynx is invaded, and finally there are produced 

 the infective metacyclic trypanosomes of the blood type. 



Lloyd and Johnson (1924) find that the trypanosomes taken into the 

 gut quickly degenerate, and can thus be distinguished from T. gambiense, 

 T. brucei, and T. congolense, which develop in this situation (Fig. 233). 

 In the labial cavity they quickly change into crithidia forms with flagella 

 and become attached to the walls in compact colonies. When a colony 

 is small the flagellates are short and boat-shaped, and when it is large 



I. 36 



