INFUSORIA 



793 



forms are common, and by means of these the infection is transferred 

 to new hosts. 



Although long believed to be harmless, pathological lesions have 

 been found by Strong and others in man and monkeys, consisting of 



* 



FIG. 198. BALANTIDIUM COLI IN A FOLLICLE OF THE COLON, BREAKING THROUGH 

 THE MUCOSA. (Army Med. School Collection, Washington, D. C.) 



thickening and ulceration of the infected intestine, with penetration 

 of the balantidium through the gut wall to the subserous layer. Exten- 

 sive lesions may be found at autopsy, even in the absence of a his- 

 tory of dysentery or diarrhea. 



CHLAMYDOZOA 



There is a small group of very minute intracellular organisms 

 which are believed by many to be protozoa, and for them von Pro- 

 wazek has created the class named ' * chlamydozoa. " He believes that 

 such organisms produce smallpox, vaccinia, hydrophobia, trachoma, 

 scarlatina, Molluscum contagiosum, avian plague, the contagious epi- 



