1910.] The Development of Trypanosomes in Tsetse Flies. 379 



infected. They were then pooled and injected into a healthy monkey, which 

 became infected with Sleeping Sickness. This shows that the infected fly 

 may escape detection by the microscope. 



In Experiments 1269, 1452, 1672, 1680, 1693, and 1706, flies were found 

 containing flagellates. These flies had not given rise to disease in the monkey 

 they had been fed on, nor did their injection prove successful. The 

 flagellates must be considered to be Trypanosoma gambiense, and therefore a 

 cage of flies may become infected without causing disease either by biting or 

 injection. 



In Experiments 1549 and 1602, flies were found containing flagellates, and 

 these flies succeeded in infecting monkeys both by biting while alive and 

 injection after death. 



Lastly, in Experiments 1566, 1712, and 1760, flies were found with 

 flagellates which had infected the monkey fed on, but which failed to give 

 rise to disease when their body-contents were injected into healthy animals. 



In these experiments 746 laboratory-bred flies were used. Thirty-nine 

 became infected — that is to say, more than 5 per cent. 



C. The Development of Trypanosoma dimorphon in Lake-shore Glossina 



palpalis. 



This is the commonest cattle trypanosome in Uganda. During 1909 it 

 caused epidemics among the Government transport oxen at Entebbe, 

 Mr. Walsh's cattle at Kabula Muliro, and the Uganda Company's cattle at 

 Namukekera, all of which were investigated by the Commission. 



The name Trypanosoma dimorphon is used for this species, although two 

 forms have not been found. It belongs to the short, stumpy type of trypano- 

 somes, without free flagella, and is probably identical with that found in 

 Zanzibar by Edington ; in Portuguese East Africa, described by Theiler ; in 

 Northern Ehodesia by Montgomery and Kinghorn ; and in Southern 

 Ehodesia by Bevan. 



Table V. — Development of Trypanosoma dimorphon in Lake-shore Glossina 



palpalis. 



Experiment. 



No. of flies. 



No. of 

 dajs fed on. 



No. of days before 

 flies became infective. 



No. of days flies 

 remained infective. 



574 



500 



3 



21 



21 



996 



100 



3 







1 1010 



120 



3 







1022 



100 



3 







