SPIROTRICHA, HETEROTRICHA 



639 



Balantidium coli is a very common parasite in the intestine of 

 pigs, and also in chimpanzee and orang-outang. In pigs, the ciHate 

 ordinarily confines itself to the lumen of the intestine, but according 

 to Ratcliffe (1934), when the host animals become infected by an 

 organism belonging to Salmonella, it invades and ulcerates the in- 

 testinal wall. The cysts developing in pigs appear to become the 



*i..:^ 



3 4 



Fig. 301. Balantidium coli, X530 (Kudo). 1, a living trophozoite; 



2, a stained trophozoite; 3, a fresh cyst; 4, stained cyst. 



chief source of infection, since balantidial dysentery is more com- 

 monly found among those who come in contact with pigs cr pig in- 

 testine. The cysts remain viable for weeks in pig faeces in moist 

 and dark places, though they are easily killed by desiccation or ex- 

 posure to sun light. The cysts may reach human mouth in food or in 

 water contaminated with them, through unclean hands of persons 

 who come in contact with faeces or intestine of pigs, and in some 

 cases perhaps through uncooked sausage. 



B. sids McDonald. Ellipsoid; 35-1 20m by 20-60/i; macro nucleus 

 more elongate than that of B. coli; in the intestine of pigs. Levine 

 (1940) through a series of culture studies, has come to consider that 

 B. coli and B. suis are only morphological variations due to the 

 nutritional condition and that B. suis is synonymous with B. coli. 



Other domestic and wild animals harbor various species of Bal- 

 antidium. 



