PROTOZOA 183 



hours. The skin around the point of inoculation becomes 

 gangrenous, and foul-smelling edema, with gas-containing 

 blebs, occurs. 



Habitat. It is a common inhabitant of the intestines of 

 man and animals, and if found in water, is a sure indication 

 of sewage pollution. 



CHAPTER XX 

 PROTOZOA 



PROTOZOA are unicellular animal organisms, minute as bac- 

 teria, and differing from bacteria in the methods of repro- 

 duction. Their structure and functions are more complex, 

 although the borderland is ill denned. 



Fig. 112. Pure culture of trypanosomes of mosquitoes Crithidia fas- 

 ciculata. Multiplication roset showing large and small cells. Nine-day 

 culture (Gen. i. x 1500) (Novy, MacNeal, and Torrey). 



Divisions. There are four grand divisions of protozoa: 

 (i) Sarcodina, containing 5500 species; (2) mastigophora, 



