AMID THE SNOW PEAKS OF THE EQUATOR 



275 



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Photo by Prof. William M. Davis, Harvard University 

 ON THK ZAMBEZI 



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. 



IT IS CARRIED BY THE TSETSE-ELY 



Trypanosoma gambiense has been 

 found in West Africa from about 15 0 

 north to 15 0 south latitude; it is widely 

 spread in the Congo basin, reaching a 

 point about 11 0 south in the Lualaba 

 River ; it is found in the Tanganyika re- 

 gion and in Uganda and along the Nile 

 as far as 6° north latitude. But its dis- 

 tribution 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. 



Nothing is known of the life history 

 of the trypanosome, and it is impossible 



at present to make a dogmatic 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 sense and not as 

 a simple mechanical transmitter. 



It has been proved beyond question 

 that the infection is transmitted by a 

 species of tsetse-fly (Glossina palpalis), 

 but it is not definitely known that it is 

 never transmitted by other species as well. 

 It has been stated that a species of mos- 

 quito (Stegomyia sp.) is also capable of 

 transmitting trypanosomiasis. 



The disease affects individuals of all 

 ages and of both sexes. Males, perhaps, 

 more often contract the disease than fe- 

 males, because they are more constantly 

 exposed to the attacks of tsetse-flies dur- 

 ing the course of their occupations as 

 paddlers, fishermen, etc. 



