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Mammalian Trypanosomes of Africa 
the 1912 fly-strains and were overlooked, it must be remembered that attention 
was first drawn to the peculiarity of the 1920 buck strain by its movements 
and by the way in which it killed its monkey host, and that posterior-nuclear 
forms were at once seen in the first guinea-pig inoculated. Years of experience 
have made me familiar with the behaviour of the local green Cercopithecus 
in captivity, but the disease in this animal was something I had not seen 
before. 
(15) It is highly improbable that the newly recognised strains of trypano¬ 
somes could have been introduced by such poachers as have visited the 
islands since the depopulation. These people go to fish, and do not take 
dogs or stock with them. It appears reasonable , therefore , to regard this newly - 
recognised brucei -like organism as a strain or variety of the older and formerly 
more common trypanosome whose general behaviour so strongly resembled the 
human parasite , T. gambiense. 
(16) The situation presented by the uninhabited fly-area in Uganda is 
unparalleled in Africa, and amounts to a demonstration, on a colossal scale, 
of the effects of environment on a strain of trypanosome. Before the epidemic, 
when the islands were teeming with natives and stock, the main food-animals 
of the G. palpalis were undoubtedly reptiles and man and his domestic animals. 
Reliable native accounts agree that the situtunga were comparatively rare 
in the palmy days of Sesse, and were seldom seen save on the extreme southern¬ 
most islets, whither great parties went at intervals to hunt them. The antelope 
may thus be regarded as an almost negligible source of food to the fly before 
the epidemic. The revolutionary change in the economy of the fly, effected by 
the sudden wholesale removal of man from its reach, has, with the passage 
of years, resulted in the usurpation by the antelope of the position formerly 
occupied by man and his stock. Among the reptiles, as Carpenter has pointed 
out, the result of the change has probably been a great increase in Varanus, 
more or less at the expense of the crocodile; for the natives prized Varanus 
skins very highly for their drums, and this lizard is very fond of crocodile 
eggs. 
(17) Whether man or his stock or the antelope carried polymorphic 
trypanosomes in the days before the epidemic we shall, unfortunately, never 
know. We must, however, admit that the occurrence of human trypano¬ 
somiasis in the Uganda Lake area before 1899-1900, however probable it 
may be in theory, is not supported by native evidence. At all events, the 
existence of a human disease presenting the symptoms of the “mongota” of 
the epidemic is denied alike by the Baganda and the Basoga and the Basesse. 
(18) It appears significant that the most virulent strain of trypanosome 
so far isolated was recovered from Damba Island, for on this island the fly 
and antelope are in more intimate relation than anywhere else. Both are 
very numerous, and the topography of the island entails constant exposure 
of the animals to fly-bite. Here, too, the effects of the close feeding of ever- 
increasing numbers of antelope are not yet pronounced. As Fiske was the 
