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156 Kinghorn and Yorke have since proved to be transmitted by Glossina morsitans.

Meanwhile Chagas had associated a disease, occurring in Brazil, with a peculiar species of trypanosome, Schizotrypanum cruzi, having a special transmitter, Lamus (Conorhinus) megistus. (See p. 188.)

Geographical distribution.—The presence of T. gambiense has been definitely ascertained for the west of Africa from the Senegal in the north to Mossamedes and the upper reaches of the Lualaba in the south. Also in the Niger and Congo basins, and in Uganda, where it must have been introduced only recently, apparently about the end of the nineteenth century. Throughout this vast area the infection is not uniformly distributed. It occurs

Fig. 43.—Schema of trypanosoma, with nomenclature.

in a patchy way, principally along the banks of the rivers and shores of the lakes, conformably to the distribution of certain tse-tse flies, and apparently being influenced also by the frequency and nature of the intercourse and by the occupations of the inhabitants. There is strong reason for believing that the recent influx of Europeans into tropical Africa and the consequent increased movement of the natives is spreading the disease, and that this extension has by no means reached its limit. As regards the eastern side of the continent, the disease has not extended beyond the shores of the Victoria Nyanza. In this locality its present limits are Wadelai on the Nile to the north, and the southern end of Lake Tanganyika to the south. There is every reason to apprehend that, in time, the distribution of trypanosomiasis will become coextensive with that of the appropriate tse-tse flies.