PROTOZOA 205 



the sleeping sickness of Africa, which is very fatal for human 

 beings. About 60 species have been described, and 10 dis- 

 eases are believed to be due to this form of organism. 



Morphology. A fusiform mass, containing at one end a 

 flagellum (Fig. 103). 



In the living state these protozoa are very motile. In the 

 stained specimen chromatin granules are found and two or 

 more nuclei. From the smaller nucleus arises the undulatory 

 membrane, which passes into the flagellum and assists in the 

 wave-like motion. 



Fig. 103. Pure culture of trypanosomes of mosquitos Crithidia 

 fasciculata. Part of roset of elongated crithidia with flagella directed 

 centrally (Gen. 39 X 1500) (Novy, MacNeal, and Torrey). 



In the body fluids division occurs, first of the nucleus and 

 then of the protoplasm. 



Cultivation. Novy and MacNeal have succeeded in culti- 

 vating these protozoa on blood-agar, and multiplication goes 

 on rapidly, so that rosettes are formed with the flagella ar- 

 ranged around a common center. (See Figs. 102, 103, 104.) 



Trypanosoma Lewis! (Kent, 1878). Found in rats by 

 Lewis; not fatal to them, though often equaling the red cor- 

 puscles in number. It was one of the first of this group to 



