CHAPTER XVIII 



EXAMPLES OF PARASITIC INFUSORIA 



TECHNICAL SUGGESTIONS 



Our native frogs furnish the most convenient single source of 

 material for the study of parasitic Protozoa. Representatives of the 

 genera Nyctotherus and Opalina are almost always present and a 

 species of Balanlidium is not uncommon. The examination of living 

 material should be supplemented by study of permanent mounts. 



Motile and encysted specimens of Balantidium are readily obtain- 

 able by examining fresh fecal material from hogs or by bringing to the 

 laboratory freshly removed sections of the caecum and colon of hogs 

 from slaughter houses. The organisms will remain alive for days at 

 room temperature. Sections of heavily infected specimens will show 

 numerous parasites in situ. Guinea-pigs occasionally harbor repre- 

 sentatives of this genus, as do also cockroaches. 



Where there is opportunity, some of the bizarre forms of ciliates from 

 cattle and other ruminants should be demonstrated. 



CHARACTERISTICS OF THE INFUSORIA 



The Infusoria are Protozoa of definite form whose locomotory 

 apparatus is constituted by a more or less considerable number 

 of vibratile cilia on the surface of the body and which typically 

 possess two forms of nuclei — a vegetative macronucleus and a 

 much smaller reproductive micronucleus. In the subclass 

 Opalinata the two or more nuclei present are of a single type. 

 The transfer to new hosts is through formation of cysts. These 

 may be purely protective, but in some forms multiplication 

 occurs. 



Many parasitic Infusoria are to be found in the higher animals, 

 but in so far as is known they do not usually play an important 

 role as pathogens. One species, Balantidium coli, is a widespread 

 and serious parasite of man. Several species occur as ectopara- 

 sites of fish and are often the cause of serious epizootics. As 

 an introduction to the group, we shall study the infusorian 

 parasites of the frog which harbors representatives of two genera, 

 Nyctotherus and Balantidium, reported as infecting man. 



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