482 MITZMAIN. 



number of resting flies. One lizard consumed in three minutes 

 68 flies by actual count. 



This condition, needless to say, rendered unfeasible any scheme 

 of experiment except that involving direct mechanical trans- 

 mission. Therefore, this course of experimentation was not 

 pursued beyond a forty-eight-hour period. 



Horses H-4, 269, and H-3 have showed no evidence of in^ 

 f ection. The usual tests for the presence of trypanosomes were 

 applied, such as registration of temperatures, blood examina- 

 tions, and guinea-pig inoculations, and all with negative results. 

 The blood of the horses was examined daily for thirty days. 

 Their temperatures were taken during a course of forty-three 

 days. No reaction was noted. Two cubic centimeters of blood 

 from each of the 3 horses were inoculated into 2 guinea pigs 

 on April 1, at which time no organisms were seen by micro- 

 scopic examination. The 6 guinea pigs were examined for 

 trypanosomes daily for a period of thirty-five days. They were 

 negative upon every occasion. Horse 269 died June 13, 1912, 

 from an unrecognized cause believed not to be surra. Horses 

 H-4 and H-3 were alive and free from surra on August 15, 1912. 



EXPERIMENTS WITH GUINEA PIGS IN A GLASS JAB. 



In the following experiments closer observation was made 

 possible by the use of the largest museum jars obtainable, which 

 were screened with close-meshed surgical gauze. (Plate II.) 



The method employed was to immobilize a closely cropped 

 surra guinea pig on a wire frame, place it in the jar with a known 

 number of laboratory-bred Stomoxys, and replace it at stated 

 intervals, after the flies had fed voluntarily, by a healthy animal 

 similarly prepared. The exchange was made by the aid of ether, 

 the jar being lightly etherized so that flies near the opening would 

 be driven back, and those feeding upon the animal stupefled. 

 The new animal was prepared during the interim and substi- 

 tuted while the flies in the jar were still under the effects of the 

 ether. In the substitution of one host for another the flies re- 

 covered from the anaesthetic within a few minutes, in each 

 instance by the time the new animal was introduced and the jar 

 screened. In the case of guinea pig 81, 6 flies commenced feed- 

 ing on the new host in less than five minutes after the surra 

 guinea pig was withdrawn from the jar. 



The experiments were conducted during the daytime, begin- 

 ning as early as practicable and ending before twilight. The 



