Page:Transactions of the Royal Society of Tropical Medicine and Hygiene, volume 1.djvu/48

 the Arabised negroes inscribed the history of the Muhammadan Mandingo kingdoms round the sources of the Niger, sleeping sickness has been a known disease, occurring sporadically here and there, but never to such an extent as to create widespread alarm or serious depopulation. It scarcely bore this devastating character even in the early 'eighties, when it affected the Lower Congo. Indeed, the records of the Baptist Mission at San Salvador, etc., would seem to show that sleeping sickness has come back there from the east, from the inland basin of the Congo, and is afflicting the country far worse than it did in the 'sixties and 'seventies. The matter is really becoming very urgent for those who take an interest in the commercial development of Africa, as the spread of the disease is attaining such proportions as may almost end in the depopulation of the Congo basin, to say nothing of the unchecked ravages in the Uganda Protectorate. Its range certainly seems to be limited by the range of one or more species of tsetse fly that do not care about parts of Africa without heavy rainfall and abundant vegetation.