172 ENTOMOLOGY FOR MEDICAL OFFICERS 



one, since a fly becoming polluted and dangerous by feeding 

 on an infected animal very soon becomes innocuous, and 

 after remaining innocuous for several weeks again becomes, 

 and remains for several months, infective. Later, the 

 exact experiments of Bruce and his staff, while corrobor- 

 ating Kleine, have brought numerous facts to light, among 

 which the most important are (i) that only a very small 

 percentage of flies experimentally fed on infected animals 

 ultimately become infective ; and (2) that the infectivity of 

 this small percentage depends upon a delayed infection of 

 their salivary glands. Bruce and his coadjutors have followed 

 out the actual development of the trypanosome in the (small 

 percentage of) infected flies that ultimately become in- 

 fective ; they have observed that the trypanosomes multiply 

 most actively in the gut, but they have not yet succeeded in 

 tracing their route to the salivary glands. 



Prophylactic measures against G. palpalis are discussed by 

 Bagshawe in the exhaustive account of the species published 

 by him in the Bulletin of the Sleeping-sickness Bureau for 

 January 1909. Since both the adult and the pupa are 

 naturally found only in shade near the edge of water, he 

 recommends the eradication of scrub and the free lopping 

 (not necessarily felling) of large trees, for a distance of not 

 less than 30 yards from the water's edge in infested places 

 where natives congregate. It is the method of the prophets 

 in dealing with the groves and high places of Baal and 

 Ashtoreth. The eradicated scrub, etc., should be either 

 removed or burnt on the spot, and the cleared ground should 

 be stirred to expose any buried pupae to the action of the 

 weather and to the attacks of insectivorous birds. In support 

 of this measure Bagshawe shows how deforestation in certain 

 areas once infested has by the consequent desiccation of the 

 soil incidentally led to the disappearance of the fly. 



Bagshawe thinks that the collection of pupa: and the 

 trapping of flies is like the labour of Sisyphus, son of .^olus ; 

 but elsewhere he mentions how a planter in the island of 

 Principe caught large numbers of the flies by clothing natives 

 in black cloth smeared with bird-lime. The proceeding is 

 simple and direct, and is therefore not abundantly justified 

 by any analogy, but it should certainly not be condemned 



