502 MITZMAIN. 



EXPERIMENTS ON CYCLICAL DEVELOPMENT. 



The first of this series of experiments was conducted with a 

 small number of wild flies at a time when bred flies were not 

 available. The experiment was followed out to completion mainly 

 to acquire a technique for keeping flies alive under laboratory 

 conditions. In this respect the tests were successful. The flies 

 were kept individually in glass tubes and fed daily until the 

 last fly of the original lot died. Fourteen flies were used on 

 the first day after infection by one bite per fly on a heavily 

 infected guinea pig (45). The duration of the experiment was 

 sixty-seven days from the initial infective feeding. The sole 

 survivor was too enfeebled to feed on the sixty-eighth day, when 

 it was inoculated in a subcutaneous pocket of a healthy guinea 

 pig. Fifty days elapsed without any infection resulting; there- 

 fore, it was assumed that the feeding experiments were negative. 



Two other experiments were tried with laboratory-bred flies 

 with the object of using as many flies as possible at once. 

 Large bottles were utilized into which the monkey's tail was 

 introduced to be fed to the flies. The stock of flies rapidly 

 diminish until the twenty-eighth and thirtieth days. 



Prior to the beginning of the first experiment (Table X), 

 the flies were applied for two days on monkey A, which upon 

 both occasions had only a very few trypanosomes in each field of 

 blood examined. Trypanosomes were seen in emulsions of 3 flies 

 of this series on the second day of biting the infected monkey. 



The flies used in the second of these experiments (Table XI) 

 were fed twice on the blood of surra monkey R. At each 

 feeding a moderate number of trypanosomes were present in 

 its blood. A single fly which was injured after feeding on 

 monkey R showed a large number of surra-like flagellates in 

 an emulsion of its intestinal tract. 



In one instance the survivors of the experiment were inocu- 

 lated into guinea pigs to test the presence of infective organisms. 

 These animals did not react. The other experiment ended on 

 the thirty-first day with the death of the last 2 flies of the 

 original 75 flies which had been applied to guinea pigs at the 

 beginning of the experiment. 



None of the guinea pigs and monkeys employed in the series 

 was used for other purposes until forty-four days after the 

 completion of feeding by the flies. During this time the animals 

 were examined at convenient intervals, but no indications of the 

 infection were encountered. 



A final experiment to complete the series was made one month 

 later with laboratory-bred Stomoxys, kept individually in suit- 



