HOST-PARASITE RELATIONS: INTESTINAL PROTOZOA 



cecum into the ileum of rats and other animals. When 

 trichomonads are fed to experimental animals move- 

 ment of the trophozoites appears to be more or less in- 

 hibited in the anterior part of the small intestine but 

 gradually regained as the organisms approach the cecum 

 (Hegner, 1924a). The factors that cause cessation of 

 movement in the duodenum and jejunum are, of course, 

 sufficient to render these habitats untenable for the 

 flagellates. 



The blood stream. Many reports have been published 

 of the presence of intestinal flagellates in the blood of 

 various animals. Among these are listed trichomonads. 

 For example, Lanfranchi (1908) found trichomonas in 

 the blood of a pigeon, Plimmer (1912) in the blood of 

 snakes, Sangiorgi (1922) in the blood of a mouse, and 

 Pentimalli (1923) in the blood of man. Kessel (1925a) 

 found T. hominis in the pus of an amoebic liver abscess 

 and believes that it reached this location by vi^ay of the 

 blood stream from the intestine, but had no evidence on 

 this point except the presence of the organism in the 

 liver at a distance from its normal habitat. In most of 

 these cases the trichomonads were found at autopsy and 

 there was some danger of contamination, as well as 

 opportunity for the flagellates to enter the blood stream 

 in some way after death. It does not seem safe at present, 

 therefore, to state definitely that Trichomonas ever lives 

 in the blood stream of man or any other animal while 

 alive. 



Factors within the intestine. What conditions within 

 the large intestine of man are favorable for the growth 

 and multiplication of Trichomonas hominis? Tempera- 



148 



