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., Monadida, 
and one important family, viz., Trypanosomidae. 
THE TRYPANOSOMAS. 
TRYPANOSOMA Evansr (Borer. soma—body) 
(Evans). 
ffistory.—Discovered in 1880 by Evans. 
Distribution.—Found in India, Bombay, Southern 
China and Indo-China, Philippine Islands. 
Description.—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. 
Lite 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- 
