^IV] TRYPANOSOMIASIS , 233 



between developmental forms of ingested trypanosomes and 

 the various insect flagellates. 



It has been shown repeatedly that when Tabanidae, inter- 

 rupted in a feed on an infected animal, are at once transferred 

 to a healthy one, the latter may become infected as a result of 

 their bites. In these cases the parasites, present in the blood, 

 are simply mechanically transferred from the first animal to the 

 second by means of the proboscis of the insect. Almost any 

 blood-sucking insect is capable of such transference of in- 

 fection, but the importance of this mechanical transmission 

 should not be under-estimated. 



With the exception of El Debab {T. soudanense) , there now 

 seems little doubt that the pathogenic trypanosomiases of 

 Africa are all transmitted by various species of Glossina, which 

 serve as the true invertebrate hosts and, once infected, remain so 

 for considerable periods. On the other hand, there is evidence 

 to shew that these diseases, once started, may continue to spread 

 in the absence of tsetse-flies. 



In this connection the outbreak of Trypanosoma pecorum 

 infection in a herd of cattle belonging to the Uganda 

 Sleeping Sickness Commission is of some interest, for there 

 seems to be little doubt that in this case Tabanus secedens 

 Walk, was responsible for spreading the infection. The herd 

 contained a few animals that had been experimentally infected 

 with T. pecorum. Shortly after the appearance of swarms 

 of Tabanus, large numbers of the cattle, that had remained 

 healthy for a year, shewed signs of infection with T. pecorum. 

 It should be noted, however, that Glossina palpalis were also 

 found in small numbers after the Tabanids had disappeared, 

 and their presence might have been overlooked previously. 



Jowett made some experiments near Cape Town with a 

 cattle trypanosome of the Dimorphon type, obtained near Beira, 

 Portuguese East Africa. As this infection seems to spread in 

 the absence of tsetse-flies, transmission experiments were made 

 with HcBmatopota and Stomoxys. 



" Numbers of Rcematopota and Stomoxys were coUected at 

 frequent intervals and placed in large glass lamp chimneys, the 

 ends of which had been closed with mosquito netting. After 



