36 INTESTINAL CILIATES OF MAN 



E. Intestinal Ciliates of Man 



L Classification. The ciliates belong to the class Infusoria. 

 The members of this class are characterized by the presence 

 of locomotor organs in the form of cilia. Most of them 

 are free living. Many parasitic species occur in vertebrates 

 and invertebrates, but only one species, Balantidium coli, 

 has been found with frequency in man. Other species have 

 been recorded from man but not often enough to warrant 

 their inclusion here. 



2. Description of species, a. Balantidium coli (Plate IV, 

 Fig. 1) : This is a very large Protozoon, measuring from 60 

 to 100 microns in length and from 50 to 70 microns in breadth. 

 It is oval in shape and covered with cilia arranged in parallel 

 rows, giving it a striated appearance. The macronucleus 

 is large and bean shaped and near it lies a small spherical 

 micronucleus. At the anterior end is a funnel shaped 

 peristome, and at the posterior end a terminal cytopyge 

 (anus). Two contractile vacuoles are present. Repro- 

 duction is by binary fission. Conjugation and encystment 

 occur. 



6. Nyctotherus: Three species of this genus have been 

 reported from man but are so rare that they need not be 

 .described here. 



3. Method of diagnosis. There is nothing in fecal material 

 that is likely to be confused with these ciliates on account 

 of their large size and distinctive characteristics. A species 

 that may be Balantidium coli is abundant in the intestine 

 of the pig and another species occurs in the rectum of the 

 frog. A species of Nyctotherus lives in the rectum of the 

 frog and another species in the rectum of the cockroach. 

 Anyone wishing to study these parasites can easily obtain 

 them from these animals. 



