INTESTINAL FLAGELLATES OF RATS 139 



definite symptoms of diarrhea and even fatal dysentery were pro- 

 duced. Pathological conditions resulted whether the infection was 

 a natural one or an experimental infection from other kittens, from 

 man, from the monkey or from the rat. The writer believes that 

 Kessel's ''T. parva' is the P entatrichomonas of the rat since his 

 figure resembles that species in all respects except in the number 

 of flagella and they are usually difficult to count. The writer also 

 believes that his trichomonads of man, monkey and kittens are this 

 sd^mo. P entatrichomonas. Wenyon (1915) says, "Dr. A. C. Steven- 

 son has shown me a section of the caecum of a mouse in which 

 there is a definite lesion of the mucous surface which is being in- 

 vaded by numerous Trichomonas." (The species is not mentioned 

 but may be P entatrichomonas.) 



Phagocytosis of Trichomonas felis by polynuclear leucocytes 

 has been reported by Cunha and Muniz (1922) and they interpret 

 this phenomenon as a protective action on the part of the host. 

 The writer has seen the same phenomena in the living condition, 

 that is, a Pentatrichonionas of the rat ingested by a leucoc)1:e, and 

 in prepared slides has seen the Pentatrichonionas of man that had 

 been ingested by leucocytes. Perhaps the Trichomonas felis of 

 Cunha and Muniz is the same as the Pentatrichonionas of man 

 and the rat. 



The Chilomastix of the rat is, apparently, without any patho- 

 genic effect upon its host, but no extensive studies have been made 

 to determine this point. 



Giardia was believed not to cause diarrhea in rats by Boeck 

 (1919). The same author denied any pathological effects on 

 meadow mice by G. microti although Kofoid and Christiansen 

 (1915a) believed that G. microti caused inflation and discolora- 

 tion of the intestine of mice and that G. muris (1915^) caused dis- 

 coloration and flaccidity in the intestine of mice at the point of 

 infection. Giardia is definitely pathogenic to rats and mice accord- 

 ing to Fantham and Porter (1916) and Galli-Valerio (1924). The 

 possible pathogenic role of the diff'erent species of Giardia in the 

 rat needs further investigation. 



J. Relation to other hosts 



One of the most interesting problems in parasitology is that per- 

 taining to host-parasite specificity. Hegner (1928c) believes that 

 each species of parasite is, as a rule, limited to one species of 



