NAGANA OR TSE-TSE FLY DISEASE 



657 



end is usually blunt, and the body often contains granules in the anterior 

 portion of its protoplasm. It divides longitudinally, and, according to 

 Bradford and Plimmer, a form of longitudinal conjugation occurs in the 

 blood. According to the same observers, it can be kept alive for five to 

 six days in blood outside the body. It is less resistant to the action of 

 cold than Tr. lewisi, perishing in a few days at 5 to 7 C., but, like the 

 other organism, it can withstand short exposures to temperatures down to 

 - 191 C. ; it is quickly killed at 44 to 45 C. Novy and MacNeal suc- 

 ceeded in cultivating this trypanosome also, though here it was very 



FIG. 188. Trypanosoma brucei from blood of infected rat. Note in 

 two of the organisms commencing, division of micronucleus and undu- 

 lating membrane, x 1000. 



difficult to obtain a first 'growth from the blood on their blood-agar 

 medium ; once started, however, it was kept alive through many sub- 

 cultures, the optimum temperature of growth being 25 C., and it was 

 from these sub-cultures that the infection was obtained which definitely 

 proved the organism to be the cause of the disease. In cultures, as with 

 Tr. lewisi, short forms occur, and there is sometimes a rosette formation 

 with the flagella directed outwards ; agglutination phenomena are also 

 observable in defibrinated blood. Under favourable conditions, involution 

 forms occur, the organism dividing frequently to form round flagellated 

 individuals. 



Nearly all laboratory animals are susceptible to infection, and the 

 42 



