APPENDIX B 287 



sense, and not as a simple mechanical transmitter; 

 that the trypanosome, after entering the intestinal 

 canal of the insect, undergoes developmental changes 

 requiring a considerable space of time for their com- 

 pletion, developmental changes which enable it sub- 

 sequently, when the opportunity occurs, to effect a 

 lodgment in the human or other vertebrate host. 

 Considering the bionomics of Glossina, it seems not 

 improbable that the trypanosome, after undergoing 

 certain unknown changes, enters the larva, and is 

 thus transmitted by heredity to the vertebrate host ' 

 (Manson). 



It has been proved beyond question that the infec- 

 tion 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 mosquito {Sfegomyia^ 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 females, because they are more constantly 

 exposed to the attacks of tsetse-flies during the course 

 of their occupations as paddlers, fishermen, etc. 



The incubation period of trypanosomiasis has been 

 found experimentally in animals to be two or three 

 weeks, and it is probably the same in man. 



The symptoms usually begin with a fever of an 

 irregular and indefinite character. In some cases it 

 lasts for a few days, and recurs after a longer or 

 shorter interval ; in other cases it may last for weeks, 

 with an equally long interval between the periods. 

 The degree of fever is also exceedingly variable. The 

 patient becomes enfeebled by the attacks, and becomes 

 anaemic. The cervical and other glands become 

 enlarged and sometimes tender. Occasionally they 

 resume their normal size either temporarily or per- 



