XVIII] TRANSMISSION 



intestinal infection, and it only occurs when the trypanosomes 

 in the gut have reached a certain stage of development, and 

 even then only when the conditions of temperature are suitable 

 for the further development of the parasites. It was found 

 that on every occasion on which the salivary glands were infec- 

 tive, the trypanosomes in the intestine were also virulent 



As a large number of the wild game harbour T. rhodesiense, 

 in nature the fly is frequently infected. In the Luangwa 

 Valley, Kinghorn and Yorke found that about 0-18 per cent, of 

 the morsitans were infected with rhodesiense. 



Recently, however, Taute has published an important 

 paper in which the validity of these results is questioned. 

 This investigator carried out experiments at Lubimbinu, 

 Portuguese Nyasaland, and found that a large proportion 

 (16-2 per cent.) of the big game of that district was infected 

 with a trypanosome closely agreeing with T. rhodesiense in its 

 general characters. Nevertheless this parasite was shewn to be 

 non-pathogenic for man, as Taute fed laboratory-bred Glossina 

 morsitans on a monkey infected with the wild game strain, and 

 subsequently on a number of animals and also himself. After 

 the usual incubation period the flies became infective and all 

 the experimental animals (goats, dogs, and monkeys) on which 

 they were fed became infected and died of trypanosomiasis. 

 On the other hand, although Taute fed these same tsetse-flies 

 on himself for four days after they had been proved to be infec- 

 tive for animals, yet he remained well. This experiment was 

 repeated, with the same results, and in addition the author 

 injected himself with 2 c.c. of blood from a naturally infected 

 dog, without ever developing any symptoms of trypanosomiasis. 



These results suggest that game and domestic animals may 

 not play the part in the spread of human trypanosomiasis that 

 certain authors have supposed, and trypanosomes from such 

 sources can only be regarded with certainty as factors in the 

 spread of sleeping sickness when they have been shewn to be 

 pathogenic for man. ^ oo 



