SPIROTRICHA, HETEROTRICHA 799 



cell fragments, starch grains, faecal debris, etc. The trophozoite 

 multiples by binary fission. Conjugation (Brumpt, 1909; Jameson, 

 1927; Scott, 1927; Nelson, 1934). 



The cysts are circular to ovoid in outline; slightly yellowish or 

 greenish and refractile; 40-60ju in diameter; cyst wall made up of 2 

 membranes; cytoplasm hyaline; macronucleus and a contractile 

 vacuole are usually seen. 



This ciliate lives in the colon and caecum of man and causes 

 balantidiosis or balantidial dysentery. Strong (1904) made the first 

 histological study of the infection. The organisms invade the tissues 

 and blood vessels of the mucosa and submucosa. At the beginning 

 there is hyperaemia with punctiform haemorrhages, and later vascu- 

 lar dilatation, round cell infiltration, eosinophilia, etc., develop in 

 the infected area. Finally deep-seated ulcers are produced. The bal- 

 antidial dysentery is usually of chronic type. It has a wide geograph- 

 ical distribution. In the United States a few cases of infections have 

 been observed in recent years. In the Philippine Islands, more cases 

 have been noticed than anywhere else. 



This ciliate is a very common parasite in the intestine of pigs, 

 and also of chimpanzee and orang-outang. In pigs, the organism 

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

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

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

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

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

 monly found among those who come in contact with pigs or 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. suis McDonald. Ellipsoid; 35-120/z by 20-60/x; macronucleus 

 more elongate than that of B. coli; in the intestine of pigs (McDon- 

 ald, 1922). 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 sy- 

 nonymous with B. coli. Lamy and Roux (1950) observed both forms 

 in cultures started with single individuals, and considered the elon- 

 gate suis as conjugants and the oval coli as vegetative forms. 



B. caviae Neiva, da Cunha and Travassos. In the caecum of 

 guinea-pig. Morphology (Scott, 1927; Nie, 1950). 



