TRANSMISSION OF INTESTINAL PROTOZOA 79 



onads are destroyed in the crop within from two to five and 

 one-half hours ; very few flagellates reach the stomach alive, and 

 passage through the stomach and intestine is so slow that it is 

 highly improbable that any specimens, in a viable condition, are 

 ever deposited in the feces. 



Flies of three species were fed human feces containing T. 

 hominis. Living trichomonads were recovered from the intestine 

 of Cynomyia cadavcrina from twenty-five minutes to five and one- 

 half hours after ingestion, from Musca domestica, one and two 

 hours after ingestion, and from Liicilia sericata two and three- 

 quarters hours after ingestion. When inoculated into serum-saline- 

 citrate medium positive cultures were obtained with fecal material 

 ingested by Cynomyia cadavcrina from twenty-five minutes to 

 three hours previously and by Mnsca domestica one and two hours 

 previously. 



Flies of the same three species were fed human feces infected 

 with T. hominis and watched until they vomited or defecated. The 

 vomita or feces from the flies were then examined and living 

 trichomonads were found in droppings at various intervals be- 

 tween twenty minutes and six hours after ingestion. Positive cul- 

 tures were obtained from droppings at intervals of from twenty 

 minutes to four hours after ingestion. These results strongly favor 

 the hypothesis that flies play an important role in the dissemination 

 of T. hominis. 



The host-parasite specificity of the intestinal trichomonads of 

 man and lower animals has an important bearing on the transmis- 

 sion of these organisms. Trichomonads are known to occur in 

 practically all of our domesticated mammals and birds as well as 

 in various species of cold-blooded animals with which human 

 beings are more or less associated. Separate specific names have 

 been applied to the trichomonads in these various species of hosts 

 but it is impossible to separate many of them on the basis of 

 morphological differences and cross-infection experiments must be 

 carried out before their specific identity is definitely established. 

 An amazing situation was discovered by the writer (Hegner, 

 1929^) with respect to the infectivity of the chick. It was found 

 that trichomonads from the mouth and intestine of man, from 

 the intestine of monkey and pig and the cecum of the rat, guinea- 

 pig and prairie dog, when injected into parasite-free chicks either 

 by mouth or by rectum, grew and multiplied readily in the ceca 



