PARASITOLOGY. 197 



lowest form of animal life. The single-cell parasites 

 are classified according to their structure or mode of 

 reproduction. The branch Protozoa includes three 

 classes of interest to us, — viz. Flagellata, Sporozoa 

 and Amoeba. 



FLAGELLATA. 



The class Flagellata includes single celled para- 

 sites that are provided with one or more flagella ; 

 by the aid of the flagella they are enabled to move 

 about in the liquid substances in which they exist. 

 Under this class is placed one order, viz., Nonadida, 

 and one important family, viz., Trypanosomidae. 



THE TRYPANOSOMAS. 



Trypanosoma Evansi (Borer, soma — body) 

 (Evans). 



History. — Discovered in 1880 by Evans. 



Distribution. — Found in India, Bombay, Southern 

 China and Indo-China, Philippine Islands. 



Desc7'iption. — The protoplasmic body is elongated, 

 pointed at both ends, and provided with a nucleus in 

 the center. In the posterior end is a small centro- 

 some; from this centrosome there proceeds a thread- 

 like structure which, passing the anterior end, forms 

 a long, projecting flagellum ; by this flagellum it is 

 enabled to rapidly move about in the blood. They 

 are twenty-five microns long and one-half micron 

 broad. 



Life History. — The Trypanosomas are found free 

 in the blood plasma and obtain their nourishment by 

 osmosis ; multiplication occurs by simple cell divi- 

 sion; the centrosome, nucleus, flagellum and proto- 



