TRICHOMONAS HOMINIS! DIGESTIVE TRACT 



zoites of certain trichomonads, probably including the 

 human intestinal species, are infective. They are carried 

 through the anterior portion of the alimentary canal by 

 the action of peristalsis into the large intestine. Here 

 peristalsis is comparatively weak and the current down 

 the intestine is so slow that colonization is possible. Very 

 likely the organisms react to the current (rheotropism) 

 and are able to escape being carried out of the body by 

 swimming against it. Any condition, such as diarrhea or 

 dysentery or even looseness of the bowels, that increases 

 the speed of the current in the intestine tends to over- 

 come the locomotor powers of the flagellates and to pre- 

 vent the colonization of newly ingested specimens. The 

 greater abundance of flagellates in fecal material when 

 the bowels are loose, for example, after the administra- 

 tion of a purgative, is thus accounted for. On the other 

 hand, anything that tends to bring about the production 

 of formed stools and constipation are of advantage to 

 the parasites since under these conditions they are allowed 

 sufficient time to establish themselves m the intestine. 

 The passage of the trichomonads, therefore, from the 

 mouth to their definitive focus of infection in the large 

 intestine is due entirely to the activities of the digestive 

 tract of the host. Whether or not an infection is estab- 

 lished in the large intestine is also largely due no doubt 

 to the consistency of the intestinal contents of the host. 

 The share the flagellates play in their own distribution 

 and localization within the host is thus very slight indeed. 

 That the trichomonads of the cat may migrate from 

 the rectum into the small intestine has been suggested 

 by Brumpt (1925). Migration also may occur from the 



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