164 



Dr. H. L. Duke. 



[Feb. 26, 



Monkey 401 first showed trypanosornes on the eighth day after inoculation. 

 Monkey 511 showed first 13 days after the first injection, and Goat 512 

 developed T. uniforme 10 days, and T. gambiense and T. vivax 15 days after 

 inoculation. With reference to the prolonged incubation period in the case 

 of Monkey 511, it may be noted that, in the only case where an inoculation 

 from the laboratory antelope has recently proved positive, the incubation 

 period in the monkey before trypanosornes appeared was 18 days. 



A consideration of the conditions on Damba Island affords a vivid 

 picture — a vicious circle in constant operation, only awaiting the reappearance 

 of the natives to reproduce the recent epidemic. With the exception of 

 papyrus areas, practically the whole shore line of the island is to a greater or 

 less extent fly-ridden, one portion being occupied by the famous fly-beach, 

 from which for several years some thousands of pupae have been brought 

 monthly to Mpumu. In his recent report to the Royal Society, Carpenter 

 describes an infection eft a monkey with 885 flies caught in May, 1911, on 

 this pupa ground. The situtunga are multiplying rapidly in the absence of 

 the natives, and are far less restricted in their range than formerly. The 

 common conception regarding the habits of this antelope, as being a creature 

 spending its days in the papyrus swamps where no fly are found, and only 

 visiting dry land at night to feed, does not apply to Damba. During the 

 short time I spent on the island, I frequently saw situtunga from the canoe 

 at the water's edge both morning and evening. As late as 9 A.M. I have 

 seen them feeding among the ambatch stems in places where fly were 

 numerous, and where it required constant vigilance to avoid being bitten. 

 On one occasion I observed a female on the actual pupa-beach at 8.30 A.M. in 

 the full glare of the sun. There is also a long extent of shore, where, owing 

 to comparatively recent sinking of the lake level, there is now a strip of 

 grass and bushes some 40-50 yards wide, dotted here and there with 

 ambatch trees, between the forest and the water's edge. This is a favourite 

 haunt of the situtunga, and tsetse are present throughout its extent. There 

 is therefore every natural facility for that frequent interchange of infection 

 between fly and buck which constitutes a true reservoir. 



On the neighbouring coast of the mainland, the fly are probably brought 

 into far less frequent contact with antelope. The stretches of shore where 

 fly are numerous are few and far between, and the number of antelope 

 which actually visit any given fly area would be small. On the mainland 

 also, the situtunga would probably only be available to the fly residing in 

 the immediate neighbourhood of the papyrus, and thus the most typically 

 lake-shore antelope would be denied to the fly where the latter are most 

 numerous. 



