In 1890 Nepveu, in the course of researches in Algeria on malaria, encountered these flagellates in the blood of man. He appears to have been the first to do so; but, unfortunately, his original description is vague, and his illustrations are crude. He established no definite relationship between the organisms he alluded to and the associated morbid conditions; onsequently, his observations did not receive the attention their significance deserved, although, later, he emphatically affirmed that a trypanosome has to be reckoned with as a factor in human tropical pathology.
In 1901 Forde encountered a flagellated parasite in the blood of a European suffering from an irregular non-malarial fever, in the River Gambia Colony. This parasite he showed to Button (1902), who recognized it to be a trypanosome. Later, Button found a similar organism in the blood of a native of the same colony, and suggested the name T.gambiense, which the parasite now bears. Subsequently many cases were described, both in Europeans and natives, and the association of the parasite with a peculiar form of febrile cachexia was quickly and satisfactorily established.
A great impulse was given to the study of the subject by the discovery of trypanosomes in the cerebro- spinal fluid, as well as in the blood of cases of sleeping sickness, by Castellani in Uganda in 1902. Castellani's suggestion that the parasite is the cause of sleeping sickness has been fully confirmed by Bruce, Nabarro, and other investigators, who have also shown that in Uganda the tse-tse fly, Glossina palpalis, is the transmitter of the infection, an hypothesis already advanced on analogical and epidemiological grounds by Sambon and Brumpt. Then (1909) came the important discovery by Kleine that the tse-tse fly was no mere mechanical transmitter of the trypanosome, as had been supposed, but was a true intermediate host. Later, on morphological and clinical grounds, Stephens and Fantham established the existence in Rhodesia of another species or variety of trypanosome (T. rhodesiense), which
