TUn SLEEPING SICKnMSSES 



Some boys working on an uninhabited island in Lake Victoria 

 became infected with sleeping sickness. We feel, however, that the 

 proof is not quite absolute with regard to this point. 



Yorke and Blacklock with regard to C. gambiensis find that man 

 is the principal vertebrate reservoir, with a possible secondary 

 reservoir in domestic cattle. 



With regard to C. rhodesiensis, as long as the view held that this 

 was identical with C. brucei there was no difficulty in believing that 

 the vertebrate reservoir was in such animals as the hartebeest, 

 water -hogs, and domestic dogs; but with the human, crossed 

 immunity, and serological experiments detailed on page 426, it 

 again becomes evident that these two trypanosomes are distinct, 

 and therefore the question as to the existence of C. rhodesiensis in 

 game animals must again be considered as sub judice. The con- 

 fusion has arisen by trusting too implicitly to only morphological 

 characters, and ignoring serological tests. 



In Chapters XIX., p. 388, and XXXV., p. 878, we have con- 

 sidered the tsetse in relationship to its carriage of these organisms, 

 and in Chapter XXXIII., p. 837, we have described these flies. 

 C. castellanii is spread by the agency of Glossina palpalis and 

 C. rhodesiensis by Glossina morsitans, but it is not proved by actual 

 experiment what fly carries C. gambiensis. It is assumed that it is 

 Glossina palpalis, but the subject obviously requires careful study. 



The tsetse flies obtain the trypanosomes by sucking infective 

 human blood containing the organisms, which undergo development 

 in the bodies of the flies. In due time {vide Chapter XIX.) the 

 young trypanosomes in short form appear in the salivary glands 

 of the tsetse-fly, and from these organs they pass into man when 

 the fly next feeds upon him. 



The fly appears to be the definitive host of the trypanosome, 

 but there is no evidence that the infection is passed on to the suc- 

 ceeding generation. 



From a practical point of view the bite of the infected tsetse is 

 the most important method of infection, but less important methods, 

 such as sexual intercourse, are possible and must be remembered. 



With regard to predisposing causes, race, sex, and age have not 

 been proved to have any influence, though the last two have been 

 thought to be predisposing causes. 



Occupation, however, has a considerable influence, for persons 

 who live near the shores or work along the shores of lakes and 

 streams, such as fishermen, are more liable than others to contract 

 the disease, because of the habits of the fly, while porters marching 

 through fly-zones are also liable to be attacked. 



Pathology." The trypanosome either enters the lymph-stream 

 directly after the bite of the fly, and is blocked in the lymphatic 

 glands, which it inflames, and through which it passes to the 

 blood-stream and cerebro-spinal fluid, or, less probably, it enters 

 the blood-stream first, and escapes by rupture of a capillary into a 

 lymph-gland. But the polyadenitis is not the only change induced, 



