1138 



PATHOGENIC PROTOZOA 



Multiplication in its simplest form consists of binary division, 

 though conjugation also occurs. In the feces of the host encysted 

 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. 164. 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. 



The disease is transmitted, in all probability, by ingesting the 

 cysts from swine which undergo development in the human being to 

 the cyst stage: this stage, however, is never found in human infec- 

 tions and man, therefore, is probably incapable of spreading the 

 disease. 



