176 AIDS TO BACTERIOLOGY 



not feed on ordure, but frequents the brushwood near 

 water where birds and fishes congregate, and from these 

 it derives the blood it must have every two or three days. 

 It feeds on fishes lying on the surface, hippopotami, and 

 crocodiles, its proboscis being able to pierce even through 

 elephant-hide. Glossina, fusca and mosquitoes of the 

 genera Mansonia and Stegomyia are possibly important 

 auxiliaries in conveying the disease. 



The organism may be found by direct examination of 

 a wet blood-film or in the juice of the enlarged glands. 

 The parasites are often difficult to find in the cerebro- 

 spinal fluid and blood. They may be absent from the 

 blood and present in the cerebro-spinal fluid, and vice 

 versa. 



The inoculation of monkeys with the blood or cerebro- 

 spinal fluid may detect the disease when direct examina- 

 tion is negative. A count of the white cells of the cerebro- 

 spinal fluid shows an increase in the small lymphocytes 

 (Broden and Rodhain). 



Two distinct and separate forms of sleeping sickness 

 are recognised: the Uganda form, which is violently 

 epidemic, and the variety prevalent in Nyasaland and 

 Rhodesia. The latter is almost certainly not epidemic, 

 and is caused by a different trypanosome, which is 

 carried by 0. morsitans, a tsetse-fly that appears to be 

 independent of water. 



Yorke and Kinghorn found that a large proportion of 

 the wild game in Equatorial Africa, though apparently 

 quite healthy, are veritable reservoirs of trypanosomes 

 constantly infecting the tsetse- flies who feed upon them; 

 and the tsetses in turn infect man. In the case of the 

 Rhodesian or Nyasaland form, the Inter-Departmental 

 Committee on Sleeping-Sickness concluded that * the 

 evidence is conflicting as to whether the wild animals 

 which are a reservoir of the disease affecting domestic 

 stock are a danger to man.' And further, that in the 

 case of the Uganda form ' the part played by wild animals 

 is of minor importance, as compared with that played 

 by man himself,' as a reservoir from which the fly derives 

 the infection. 



Sleeping-sickness may have a conjugal origin. Monkeys, 

 dogs, and rats are susceptible, but donkeys, oxen, goats, 

 and sheep, up to the present, have shown themselves 



