1923] Kessel: Experimental Infection of Rats and Mice 425 



4. Infections of E. dysenteriae, E. coli, and C. lafleuri have been 

 experimentally transferred from rats harboring experimental infec- 

 tions of these amoebae to other young amoeba-free rats by feeding 

 them the faeces of the infected rats. 



5. The amoebae transferred from man to the rodent host have, 

 in every ease, presented no apparent morphological or racial change 

 during the period of the experiment. 



6. Four of the rats infected with E. dysenteriae and one infected 

 with E. coli died of an apparent lung infection during the experiment. 

 During the same period, three rats uninfected with human amoebae 

 from the rat colony of one hundred and fifty animals died of the 

 same lung infection. This fact indicates that rats infected with 

 E. dysenteriae have a lowered resistance and are more susceptible 

 to the lung infection than normal rats. 



7. One of the four rats that died with E. dysenteriae showed an 

 intestinal ulcer. 



8. Infections of E. dysenteriae in rats and mice apparently 

 assume a chronic form instead of an acute form as is reported in the 

 case of kittens. 



9. Both dead and normal cysts of human intestinal amoebae may 

 be found for some hours after feeding in any part of the intestinal 

 tract of experimental rats and mice. This indicates a difference in 

 the viability of the cysts. 



10. The findings of this investigation afford evidence in favor 

 of the morphological constancy of species of parasitic amoebae, under 

 conditions of change of host, and of the possibility of transfer of 

 one species of parasitic amoebae from one species of host to another. 

 Consequently heavy suspicion is thrown on the rat and mouse as 

 possible carriers of the causative organisms of human amoebiasis. 



Zoological Laboratory, 



University or California. 



Transmitted July IS, 192S. 



