194 DISEASES DUE TO PROTOZOA 



Trichomonas. Two protozoa of a slight medical impor- 

 tance are the Trichomonas vaginalis, with its nearly related 

 varieties, T. intestinalis and T. pulmonalis, and the Lamblia 

 intestinalis. These forms may infest the vagina, intestine, 

 or lung, and cause some irritation, probably not particularly 

 inflammatory. They are held responsible oftentimes for the 

 inflammation set up by bacteria gaining entrance at the site 

 of the irritation by the protozoa. However, the vaginitis 

 and cystitis caused by the T. vaginalis are serious matters 

 in children. These are usually pear-shaped bodies, with 

 prominent nucleus and well-marked anterior flagella. The 

 trichomonas has a heavy undulating membrane. 



FIG. 64. Some of the principal forms assumed by the plasmodium of 

 tertian fever in the course of its cycle of development. (After Thayer and 

 Hewetson.) 



SPOROZOA. 



Malaria. The most important disease caused by protozoa 

 is malaria. This is an infectious disease characterized by 

 intermittent chills, fever, and sweats, with prostration and 

 progressive anemia. It is common in lowlands, where 

 stagnant water collects, or in the vicinity of slowly moving 

 water, permitting the propagation of mosquitoes. "It is not 

 communicable by contact of man to man. It is the infesta- 

 tion of the red blood cells by a parasite having three forms, 



