480 MITZMAIN. 



There were employed 26,666 flies collected from animals known 

 to be surra-free, but the possibility of the migration of flies 

 from infected sources is not ignored. These flies were placed, 

 after they were etherized and examined, in the fly shed with 

 horse 49, the blood of which contained many trypanosomes, every 

 day during the six days of fly infestation. 



Horse 49 which was used to supply infection contracted surra 

 through subcutaneous inoculation March 8, 1912, of the blood 

 of bull 3148, a carabao strain of infection. The blood in- 

 oculated from the bull into the horse contained an average of 

 8 trypanosomes to 30 fields. The incubation period of the disease 

 in horse 49 was six days when, on March 14, 10 trypanosomes per 

 field were seen in a drop of blood. The temperature rose from 

 37°. 8 C. on the morning of March 14 to 40°. 2 C. on the evening 

 of that day. The following morning the temperature registered 

 39°.3 C, when blood was drawn to inoculate monkey A. This 

 animal showed a positive reaction by a rise of temperature of 

 2 degrees above normal and the presence of trypanosomes in its 

 blood upon the fourth day after injection of the blood of horse 

 49. The monkey died nine days later, showing marked ema- 

 ciation and also numerous flagellates in its heart's blood. 



During the six days of fly infestation, horse 49 did not show 

 any marked symptoms of the disease, but two days later, 

 March 22, there was a catarrhal discharge from the nose and 

 a congestion of the conjunctivse. (Edematous swellings mani- 

 fested themselves beginning April 1, when the breast and fore- 

 legs were involved. This condition became more marked daily, 

 until near the time of death when the oedema extended along 

 the abdomen and involved the genitalia. The blood of horse 

 49 showed numerous trypanosomes daily from March 15 to 

 March 20, after which time the animal was examined daily 

 until April 12 and thrice weekly from that time to the time of 

 death, which occurred May 7, 1912. The heart's blood was 

 then swarming with trypanosomes, and the lesions found were 

 characteristic of surra. 



In the present experiment the flies were placed in the cage 

 on the dates mentioned in the following numbers : 



Date. Number of flies. 



March 15 3,000 



March 16 5,000 



March 17 6,874 



March 18 3,000 



March 19 6,804 



March 20 1,988 



Total 26,666 



