266 SOME MINUTE ANIMAL PARASITES 



bacteria and amoebae. Ciliates take their share in 

 its production, for two species each of Balantidium 

 and Nyctotherus have been found in association 

 with the malady. The Balantidium is perhaps the 

 more common, and more is known about it, so it 

 will be described first. 



Balantidium coli (Fig. 50, A) is the larger of the 



B. 



FIG. 50 BALANTIDIUM COLI 



te ; B, rounded cyst of B. coli, 

 the pig 



a, Macronucleus ; b, micronucleus ; c, food particle 



A, Large free ciliate ; B, rounded cyst of B. coli, from the faeces of 

 the pig 



two species occurring in man. It is about -^ mm. 

 long, and the body is oval. If the mouth and gullet 

 are contracted, the anterior end of the organism is 

 more pointed than when they are relaxed and open. 

 The body is covered with parallel rows of cilia. 

 The macronucleus (Fig. 50, A, a] is large, and is 



