670 INFECTION AND IMMUNITY. 



stage of a trypanosome^ which multiplies in the common 

 mosquito Culex pipiens and after a complicated mi- 

 gration through the body of the mosquito is again in- 

 troduced by its bite into the blood of the owl, where, 

 after a period of sexual multiplication, it is transformed 

 into the well-known male and female halteridium." 



IT. TRYPANOSOMIASIS. 



Genus Gruby created the genus Trypanosoma in 1843, 



Trypano- . . ,, <, rr> 



NO inn. when he gave the name of Trypanosoma sangmms 

 to a flagellate protozoon which he found in the 

 blood of frogs. Since that time similar organisms 

 have been found in the bloods of many animals and 

 the genus Trypanosoma has grown to considerable 

 dimensions. It is not improbable, however, that 

 a number which now bear independent names will 

 be shown to be identical. This suggests itself par- 

 ticularly in relation to trypanosomiasis in horses, 

 in which the infections are known under four sep- 

 arate names in different countries, and the para- 

 sites are given separate specific names. The study 

 of these infections is so young and has been prose- 

 cuted in such widely separated countries that the 

 existing chaos is quite natural and can be adjusted 

 only as time and circumstances permit of close 

 comparative study. Until such a time the prevail- 

 ing views as to independence of species and of in- 

 fections must be recognized. 



Trypanosomas vary a great deal in size and mor- 

 phology. Eoughly, they are from one to five mi- 

 crons thick and from fifteen to forty-five microns 

 long, including the flagellum. All species possess 

 active eel-like movements, some traA 7 eling rapidly, 

 others slowly. A long, actively-motile flagellum 

 projects from the anterior end, and where it joins 



