200 



THE ANIMAL PARASITES OF MAN 



Order 2. Heterotricha, ciliated all over like the Holotricha, but having stouter 



cilia about the peristome. 



Order 3. Hypotricha, only ciliated on the ventral surface. 

 Order 4. Peritricha, with only a ring of spiral cilia, mostly sedentary. 



The Infusoria observed in man belong to the order Heterotricha, 

 with few exceptions. 



Genus. Balantidium, Claparede et Lachmann. 



Heterotrichous Infusoria of oval or bag-like form and almost circular on trans- 

 verse section ; the anterior extremity narrowed, the posterior end broad and 

 rounded off, or also narrowed; the peristome starting at the anterior end is 

 broadest there and becomes narrower as it gradually obliquely approaches towards 

 the posterior extremity. There are coarse cilia along the entire left border and the 

 anterior part of the right border. Longitudinal striation is distinct and regular. 

 There are two contractile vacuoles on the right, and occasionally also two or more to 

 the left. The anus (cytopyge) is terminal. The macronucleus is usually horse-shoe 

 or kidney-shaped, sometimes oval ; the micronucleus contiguous. Reproduction is 

 by binary fission and conjugation, and encystment occurs. The cysts are spherical 

 or oval. These ciliates are parasitic in the large intestine of human beings and 

 pigs, in Amphibia, and in the body cavity of polychaste Annelida. 



Balantidium coli, Malmsten, 1857. 



Syn. : Paramcecium coli, Malmsten, 1857. 



The body is oval, 60 //, to 100 /JL in length (up to 200 //, according 

 to Janowski), and 50 //, to 70 //, in breadth. The peristome is funnel- 

 shaped or contracted, the anterior end being then broadened or 



FIG. 113. Balan- 

 tidium coli. a, nu- 

 cleus ; &, vacuole ; 

 f, peristome ; d, bolus 

 of food. (After 

 Leuckart.) 



I jililil 



!i 





-LlJ 



FIG. 114. Balantidium coli, free and encysted ; 

 a, anus or cytopyge ; n, macronucleus />, bolus of 

 food. (After Casagrandi and Barbagallo.) 



pointed according to the degree of contraction (figs. 113, 114). The 

 ecto- and endo-plasm are distinct, the latter is granular, containing 

 drops of fat and mucus, granules of starch, bacteria, and occasionally 



