386 SPECIFIC MICRO-ORGANISMS 



blood of the infected animal is fairly uniform. There is, however, 

 considerable variety in size, internal structure and staining 

 properties. Multiplication takes place by unequal longitudinal 

 division, much the same as in Tr. lewisi, but the dividing cell has 

 the same general form as the others and multiple division figures 

 are less common. The larger cells are usually in process of divi- 

 sion. Trypanosomes with feebly staining cytoplasm and others 

 with very abundant coarse granules also occur. The former are 

 probably degenerating and disintegrating cells. 



Tr. brucei is taken up by the blood-sucking tsetse fly, Glossina 

 morsitans and in about 5 per cent of these it multiplies in the 

 alimentary canal and penetrates into the body cavity, causing a 

 generalized infection of the fly. After about three or four weeks 

 the salivary glands are invaded and the fly is then able to infect 

 other animals by biting them, and it remains infective for a long 

 time, probably as long as it lives. Other insects may possibly 

 serve to transmit the parasite. The infection is also readily 

 transmitted from animal to animal by the injection of infected 

 blood. 



Cultures are obtained with some difficulty, but most readily 

 by inoculating inclined blood-agar, 1 2:1, and incubating at 28 C. 

 The primary cultures should not be transplanted until they are 

 about three weeks old, and they usually fail to infect animals if 

 injected into them. The virulence is regained in the subcultures. 

 Culture filtrates are not toxic. The poison of trypanosomes 

 seems to be set free as a result of their disintegration in the body 

 fluids. 2 



Nagana occurs naturally in a great variety of the quadrupeds 

 and is usually fatal. Man is not susceptible. Mice and rats 

 die in 6 to 14 days after inoculation. Guinea-pigs may show one 

 or more relapses, the disease lasting for two to ten weeks. 



1 The agar employed should contain the extractives of 125 grams of meat, 10 grams 

 pepton, 5 grams salt and 25 grams of agar in 1000 c.c. It is liquefied, cooled to 

 50 C. and mixed with twice its volume of warm defibrinated rabbit's blood and then 

 allowed to solidify in an inclined position. 



2 MacNeal: Journ. Inf. Dis., 1904, Vol. I, p. 537. 



