506 MITZMAIN. 



The presence of surra trypanosomes in the fly has been demon- 

 strated up to forty-eight hours by several authors. The or- 

 ganism in all cases has been found in the intestinal tract and 

 never within the salivary glands and rarely in the proboscis. 

 In some instances the contents of the intestines of an infected 

 fly have given rise to the disease through inoculation into animals, 

 while in others the writer appears contented with the micro- 

 scopical findings. From a survey of the literature at hand it 

 appears that the infection was never reproduced by the former 

 method beyond twenty-four hours. 



Bruce (48) states: "a Glossina fly, a few hours after feeding on an infected 

 animal, crammed with blood showing active haematozoa under the micro- 

 scope, if minced up and injected under the skin of a susceptible animal, 

 fails to give rise to the disease (nagana) ." 



Bruce and others <49) note, in an attempt to ascertain the number of 

 tsetse flies infected with Tr. gambiense, that in one case in which no 

 trypanosomes were found in 12 flies examined, when their combined 

 contents were injected into a healthy monkey, sleeping sickness resulted. 



Bruce and others (50) injected monkeys with a single fly (Glossina pal- 

 palis) one day; 2, 3, and 4 flies two days after an infected feed. These 

 caused sleeping sickness. Between the second and twenty-fourth days after 

 infection 249 flies were inoculated, in all with negative results, although 

 15 of these flies proved microscopically to be swarming with living trypa- 

 nosomes at the time of inoculation. 



Martini (32) found trypanosoma in Stomoxys calcitrans twenty-three 

 hours after an infected meal. The organisms were not observed on the day 

 following, and they were apparently digested. 



Nabarro(i8) cites a case where trypanosomes from a mule in East Africa 

 were found in the stomach of Stomoxys as long as thirty hours after a meal 

 of infective blood. 



Button, Todd^ and Hanington(34) found trypanosomes [Tr. gambiense) 

 unchanged in the gut of Stomoxys up to twenty hours after feeding on a 

 sick horse. Also on two occasions they found fusion forms of the trypano- 

 Bome in a fly fed eighteen hours previously. 



NabarrodS) states that the organisms of sutoko, a trypanosome disease 

 of the nagana group, were found active in the stomach contents of Stomoxys 

 up to twenty-four hours after infection. 



Bruce (51) found in Uganda scanty trypanosomes in the proboscis of Glos- 

 sina m,orsitans fed forty-six or fewer hours previously on a nagana-infected 

 animal. 



Nabarro,(i8) referring to fly trypanosomiases of Uganda, recalls that or- 

 ganisms remain active for a longer time in the stomach of Stomoxys than 

 in that of Gl. palpalis. Feeding experiments with eight- and twenty-four- 

 hour intervals from infected to healthy animals were negative in Stomoxys. 

 Stomoxys was positive in direct transmission in interrupted feeding with 

 dogs. 



NabarrodS) writes that trypanosomes taken from an infected monkey 

 (Abyssinian strain of trypanosomiasis) by Stomoxys remained active in the 

 stomach for twelve hours, in that of Gl. palpalis five and one-half hours. 



