486 MITZMAIN. 



In each instance, after a lapse of six weeks to two months, the 

 experiments yielded negative results. The healthy monkeys and 

 guinea pigs used in these experiments have since been employed 

 for other experiments. 



AN ATTEMPT TO DEMONSTRATE WHETHER OR NOT A SMALL NUMBER OF FLIES 

 ARE CAPABLE OF TRANSMITTING THE DISEASE. 



Tables III and IV represent a single feeding of 1 to 3 flies 

 in an effort to determine the minimum number of flies required 

 to convey the organisms of surra. In the first series 17 experi- 

 ments were made with wild flies. The flies were fed on surra 

 guinea pig 20, and were not fed again until the time noted, a 

 range of twenty minutes to three days. 



Guinea pig 20 was used as the blood donor three days prior 

 to its death, at which time the blood swarmed with trypanosomes. 

 This animal reacted to an inoculation of the blood of a mule 

 dying from trypanosomiasis. The blood was moderately supplied 

 with trypanosomes, and at death the latter animal showed prom- 

 inent lesions of the disease. Guinea pig 20 was not examined 

 until death, on the fifty-first day after inoculation. The organs 

 showed the general appearance of surra lesions, and the heart's 

 blood fairly swarmed with trypanosomes. 



In the second series of experiments a single laboratory-bred 

 fly was permitted to feed once daily on»a new guinea pig. The 

 primary bite on the infected animal was of only three minutes' 

 duration. The fly was applied to a guinea pig heavily infected 

 with surra. This animal, guinea pig 35, was in the first stages 

 of the disease, although trypanosomes were abundant in its blood. 

 It was used previously in experiments with flies placed in a 

 museum jar. 



In this test thirty-one animals were used, each being bitten 

 once by the fly which fed until apparently satisfied. The 

 feeding with this one fly consumed thirty-one days, and the 

 experimental animals were held for examination for a period of 

 at least forty-two days prior to being declared negative. Blood 

 examinations were made daily for thirty days, after which the 

 examinations were discontinued until the day the animal was 

 employed for a new experiment. Then the examinations were 

 resumed. 



