HOST-PARASITE RELATIONS AMONG TRICHOMONADS I57 



and examination by this method (see Hegner and Becker, 1922) 

 may be accepted as yfelding most accurate results. 



Negative animals selected by this method may be given Trichom- 

 onas by mouth or by rectum, the oral route being the more suit- 

 able in attempting to determine natural transmission. 



Trichomonads to be experimentally transferred may be admin- 

 istered to the experimental animals with greatest facility by means 

 of a stomach tube, a small French catheter attached to a Luer 

 syringe being the most convenient. They may be given either in 

 dilute freshly passed feces, or in culture serum in which they have 

 been cultivated in vitro. 



PATHOGENICITY 



The question of the pathogenicity of Trichomonas is one that 

 should be considered more carefully in the future than it has been 

 in the past. Clinicians hold two opinions on this subject, one group 

 maintaining that Trichomonas may produce diarrheic symptoms 

 and the other that the TricJwmonas is nothing more than a com- 

 mensal that thrives well under diarrheic conditions. In experi- 

 mental transmission work with animals, valuable data on the effect 

 of Trichomonas on different animals may be procured. Kessel 

 (1928^) records the presence of a diphtheritic colitis in kittens 

 which appeared to be due to Trichomonas infection, and figures 

 the invasion of Trichomonas into the gut tissue in a few instances. 

 He has also recently observed a human autopsy in which the upper 

 colon and cecum of a case positive for Trichomonas exhibited the 

 same characteristic necrosis and diphtheritic colitis that he de- 

 scribed in kittens. However, there was no invasion of the tissue 

 by the trichomonads. Wenyon (1926) figures invasion of Trichom- 

 onas into human tissue taken at autopsy but was uncertain 

 whether or not the invasion was due to post-mortem change. He 

 states, however, that "guinea-pigs which are commonly infected 

 with Trichomonas cavice often show ulceration of the large intes- 

 tine and caecum with definite invasion of the tissue by the flagel- 

 late in perfectly fresh material.'' More extensive observations on 

 the effect of the presence of Trichomonas in the intestine should 

 be procured, and much important information may be obtained 

 while transmission problems are in progress. In such instances it 

 is imperative that the presence of other parasites or bacteria that 

 might produce pathogenic symptoms in the experimental animals 

 be ruled out by examination and culture. 



