286 APPENDICES 



year Button, in the Gambia Colony, found a trypano- 

 soma, which he called Tiypnnosoina gamhiense, in the 

 blood of a native suffering from fever of a non-malarial 

 character. In the same year Castellani, in Uganda, 

 discovered trypanosomes in the blood and in the 

 cerebro-spinal fluid of cases of sleeping sickness. He 

 suggested that the parasite is the cause of sleeping 

 sickness, and this has been fully proved by the 

 researches of Bruce and others, who have also shown 

 that the infection is transmitted by the tsetse-fly. 



Trypanosoma gambiense has been found in West 

 Africa from about 15° North to 15° South latitude; 

 it is widely spread in the Congo basin, reaching a 

 point about 11° South in the Lualaba River; it is 

 found in the Tanganyika region and in Uganda, and 

 along the Nile as far as 6° North latitude. But its 

 distribution is not uniform over this vast area ; it 

 corresponds with the distribution of a tsetse-fly, and 

 is thus confined to the banks of rivers and lakes, and 

 even along these it is not absolutely ubiquitous. One 

 stretch of shore is for some reason more favourable to 

 it than another. Though the trypanosome is not at 

 present found in all the districts in which the tsetse- 

 fly occurs, there is, unfortunately, no reason to 

 suppose that it has yet reached the limits of its dis- 

 tribution. By a strange irony, the opening-up of these 

 countries by Europeans, the spread of civilization, and 

 the consequent improvement in intercourse between 

 the different native races, have unquestionably been 

 largely responsible for the great increase of the disease 

 in recent years. 



Nothing is known of the life-history of the trypano- 

 some, and it is impossible at present to make a dog- 

 matic statement as to the relations which exist between 

 it and the tsetse-fly. It seems probable that the tsetse- 

 fly * serves as an alternative host in a truly biological 



