94 



TRYPANOSOMES AND SLEEPING SICKNESS 



Rhodesia in southeastern Africa occasioned by a distinct and ap- 

 parently newly originated type of trypanosome, as indicated 

 by its sudden appearance and startlingly rapid spread. This 

 type of sleeping sickness is more deadly than the older type and 

 there is reason to fear that unless efficient methods of control- 

 ling it and stamping it out are discovered it will spread over a 

 large part of tropical Africa. The disease has already spread 

 over a great part of Rhodesia, Nyasaland and Portugese East 

 Africa, and has been reported from German East Africa. There 

 is apparently a rather high natural immunity to the disease, which 

 alone is responsible for the small number of the victims. 



In the same year, 1909, a fever 

 caused by a trypanosome was dis- 

 covered by Chagas in tropical 

 Brazil, and has since been found 

 to be widely distributed there, and 

 to be the cause of much of the 

 non-malarial " fever " for which 

 the jungles of tropical South 

 America are famous. 



The Parasites. The trypano- 

 somes, next only to the malarial 

 parasites, may be considered man's 

 most deadly enemies among the 

 Protozoa. Like the Leishman 

 bodies described in the preceding 

 chapter, they are members of a 

 primitive group of the class Flagel- 

 lata, but of somewhat higher or- 

 ^nization, and probably higher in 



b. gr., basal granule; und. m., undu- the Scale of evolution. Trypano- 



t g m mem x b roSo. : n " nUCleUS; fl " fla - somes are ver y Active, wriggling 



little creatures somewhat suggest- 

 ing diminutive " artistic dolphins " (Fig. 17). They are about 25 /z 

 (about TT fotf of an inch) or even less in length, spindle-shaped, and 

 somewhat flattened from side to side like an eel. Along the " back" 

 runs a flagellum connected with the body by an undulating mem- 

 brane, like a long fin or crest. This terminates at what is really 

 the anterior end in a free tail-like flagellum. It is by means of 

 the wave motions of the membrane and the lashing of the flagel- 



