138 RESEARCH IN PROTOZOOLOGY 



fluid substances, the exact nature of which is unknown, but a 

 fluid diet is suggested. T. parva, P entatrichomonas and Hexamastix 

 frequently have food vacuoles containing bacteria, indicating the 

 nature of their diet. The P entatrichomonas of man is known to 

 ingest red blood corpuscles (Haughwout and De Leon, 1919; 

 Kofoid and Swezy, 1923), but this has not been observed for the 

 one in the rat. Chilomastix ingests bacteria of several kinds but 

 little is known as to possible limitations on the kind that it needs 

 or as to its ingestion of other than solid food. Giardia apparently 

 lacks a cytostome and so does Hcxamitus muris. They are sup- 

 posed to nourish themselves osmotically. Hexamitus pulcher fre- 

 quently shows a slit-like opening at the anterior end in prepared 

 slides but ingestion of food has not been demonstrated. The 

 cytoplasm is rather regularly filled with refractive granules which 

 Becker (1926c) took to be mitochondrial in nature, but which 

 usually stain with hematoxylin after such fixatives as Schaudinn's 

 fluid. Their exact nature is not known but they may be concerned 

 with metabolism. 



Parasites, especially the vegetable organism, Sphcerita, attack the 

 flagellates of rats, often in considerable numbers. They have been 

 seen in Chilomastix and the trichomonads but not in Giardia or 

 Hexamitus. There is much variation in the size and appearance of 

 these parasites, suggesting that there may be several species of 

 them. Becker (19266) has described some stages in the life history 

 of a Sphcerita in Endama^ha citelli, but further studies are desir- 

 able. 



These flagellates are also the prey of other protozoa of the 

 digestive tract, especially of the endozoic amoebae, as figured by 

 Wenyon (1907) and Kuczynski (1914) and as observed by the 

 writer. 



2. Pathogenicity 



Little is known as to the possible pathogenic effect of intestinal 

 flagellates on rats. So far as the writer is aware there is no evi- 

 dence for the pathogenicity of any of the trichomonads except 

 PentatricJiomonas. In many cases where this species is present in 

 any considerable numbers the contents of the cecum contain many 

 leucocytes, and it is of importance to determine whether this con- 

 dition is due to the presence of P entatrichomonas as seems to be 

 indicated. Kessel (1928/?) inoculated kittens with T. muris and "T. 

 parva." Only "T. parva" produced an infection in the kittens but 



