316 



L. A. ROGERS 



The concentrations, both of food-stuffs and products of metab- 

 oUsm, are likely to be much greater in the bottle and the results 

 may vary accordingly. 



A number of bottles containing 100 cc. of sterile water to 

 which a loopful of human feces had been added were left in a 

 20° incubator for several months. 



These bottles were used for another purpose and from the 

 earlier plates made only a few cultures were isolated. Later a 

 total colon count was made and a considerable number of cul- 

 tures isolated. In table 1 are given the results from a bottle 

 which was held at 20° for 278 days. 



The total number of colon forms decreased slowly in this 

 period. At first there was a great preponderance of B. coli 

 over B. aerogenes. Even after 100 days there were ten times 

 as many B. coli as B. aerogenes. But this relation was gradually 

 changed until at 278 days there was only one B. coli in the 40 

 cultures isolated. 



Another change which may be of some significance is found in 

 the apparent decrease in limiting hydrogen ion concentration 

 reached by the B. coli cultures. The Pg value of 5.0 to 4.8 

 observed in the first cultures isolated is normal for freshly iso- 



