1923] Kessel: Experimental Infection of Rats and Mice 415 



DISCUSSION AND CONCLUSIONS FROM TABLE 2 



1. As no young animals were available for this experiment, only 

 adult amoeba-free mice were used. 



2. One mouse only became infected with E. (liisenieriiic and only 

 one with Councilmania lafleuri. 



3. As shown by Kessel (1923?)) adult animals are more difficult 

 to infect with amoebae than young ones, and it is probable that the 

 low percentage of infection in this series of amoeba-free mice is due 

 to the advanced age of the animals. This indicates that in some cases 

 a resistance or immunity to infection is established in old animals. 



4. The cysts recovered were apparently normal and the species 

 had undergone no morphological change though passed thro\igh Ihe 

 rodent host (pis. 38-39). 



TABLE 3 

 Results Obtained from Feeding Rats with Cysts of Endamoeba coli 



DISCtTSSION AND CONCLUSIONS FROM TABLE 3 



1. No amoeba-free rats were on hand when this feeding experiment 

 was begun, so young rats were chosen, the infection of which was 

 unknown. As they had only recently been weaned it is probable that 

 the percentage of infection was low. 



2. The Councilmania found in the final examinations was in each 

 case one of the species, at that time undetermined, common to the 

 rat, and it is concluded the rats had this infection when fed with 

 E. coli. 



3. An infection of E. coli only was recovered from four of the ten 

 rats, while a mixed infection of E. coli and Councilmania common to 

 the rat was found in one rat. Thus five out of ten or 50 per cent 

 of the rats fed with E. coli- established an infection. 



