CHAPTER XIII 

 INTESTINAL FLAGELLATES IN GENERAL 



By 



Robert Hegner 



The Johns Hopkins University School of Hygiene and 

 Pubhc Health 



The mastigophora comprise a class of protozoa containing 

 large numbers of both free-living and parasitic species. It is con- 

 venient to separate the parasitic species into two groups, intestinal 

 flagellates and blood-inhabiting flagellates. The latter belong almost 

 entirely to the family trypaxosomid.e. In the following chapters 

 problems and methods of research are discussed with respect to 

 certain genera of intestinal flagellates and certain groups that 

 occur in several types of hosts. In this chapter a general survey 

 of the intestinal flagellates will be made to indicate to what orders 

 and families the more easily accessible species belong and in 

 what animals one may expect to find them. The morphology and 

 taxonomy of the mastigophora are treated in Calkins' Biology 

 of the Protozoa, pp. 248-297, and in Wenyon's Protozoology, pp. 

 268-312 and 607-715, and in Hegner and Taliaferro's Human 

 Protozoology, pp. 201-265. Calkins also gives a key to genera on 

 pp. 298-314. 



The classification of the mastigophora is a 'matter of opinion 

 among students of the group. It is customary to divide the orders 

 into two subclasses placing in the first subclass, to which the name 

 phyto:mastigixa is applied, several orders that contain plant-like 

 flagellates and in the second subclass, the zoomastigina, a group 

 of four or five orders composed of animal-like flagellates. 



Fewer parasitic species are present among the plant-like flagel- 

 lates than among the animal-like flagellates. In the order eu- 

 GLEXOiDiDA are a number of interesting species of plant-like forms 

 including Copronwuas siibtilis, which is a coprozoic species about 

 which much is known, Astasia nwbilis, which is a parasite of the 



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