1924] Kessel : Aiiwdar of Culturf Eats and Mice 521 



At the suggestion of Dr. I. C. Hall of the Department of Bacteri- 

 ology of this University, one series of rats of known amoebic infection 

 with C. nmris or C. decumani was fed on a meat diet, only, for two 

 weeks, and another series of rats known to be infected with amoebae 

 was fed only skimmed milk for two weeks. Infections were determined 

 by the epsom salt method (Kessel, 1923a). After the feeding had 

 been continued for two weeks, the experimental animals were autopsied 

 and examined for amoebae. Of the 15 rats fed on milk diet only, the 

 whole number had been cleared of amoebic infection. Of the 6 rats 

 fed on meat diet for the two weeks, 4 had been cleared of amoebic 

 infection. Nineteen amoebae-positive rats were fed on the regular diet 

 of table scraps and were used as a control. Of the previously infected 

 control rats 7 were found to have been cleared of amoebic infection 

 on terminal examination, indicating that the purgative may, at times, 

 clear some of the rats of infection, or that an active immunity may 

 arise. 



As all the rats fed on milk diet, while only two-thirds of the rats 

 fed on a meat diet, had been cleared of infection, it was considered 

 that a culture medium of high animal protein content was more suit- 

 able for the amoebae than one of higher carbohydrate content such as 

 milk. Cannon and McNea.se (1923) have shown that when meat is 

 fed to white rats the reaction of the contents of the caecum is prac- 

 tically neutral. Consequently, beef broth and brain media were pre- 

 pared and titrated to a pH of 6.35. Motile amoebae from the caecum 

 of newly autopsied animals and cysts were planted in these media, both 

 in the broth and in a 0.5 per cent agar. These were incubated at 37° C. 

 under both aerobic and anaerobic conditions. No success attended 

 these' attempts, apparently because of the putrefaction produced by 

 the rapid growth of bacteria. 



One important result derived from this phase of the work should 

 not be overlooked and that is the fact that all the rats fed on a milk 

 diet, only, for two weeks were amoeba-negative at the end of that time, 

 while of the control rats only 27 per cent were negative. It is interest- 

 ing to note that Hegner (1923) obtained reductions in the number of 

 flagellates in rats fed on a milk diet though his rats were not entirely 

 rid of the infection. 



It has been shown by Rettger and Cheplin (1921) and Cannon and 

 McNease (1923) and others preceding them that feeding milk only to 

 rats produces a change in the flora of the digestive tract from a 

 majority of gram-negative rods, presumably BacUJus roJi. to a pre- 



