GROWTH OF BACTERIA IN NORMAL MILK. 37 



Experiment No. j. December. — This experiment is a repe- 

 tition of the last two and was performed under identical condi- 

 tions. The results are shown in Tables 5 and 6 on page 36. 



The general conclusions from these tables are as follows: 



1. There was a constant increase in numbers of B. acidi 

 lactici and a tolerably constant increase in percentage. The 

 percentage in the last test reached 53.5. 



2. This sample of milk showed the presence of the species 

 called B. acidi lactici II., which were found, however, in the 

 last three tests only. 



3. B. aerogenes was not found. 



4. The Streptococcus group was present in large numbers 

 and continued to increase in number constantly throughout the 

 experiment, reaching at the end the number of two million and 

 a half. The percentage of colonies of this species also remained 

 high and, with some fluctuation in two tests due doubtless to 

 the high per cent, of undetermined colonies, was at the close 

 nearly as high as at the beginning. 



5. The two species of Sarcina increased constantly in num- 

 bers during the whole experiment, but decreased in percentage; 

 in the last test the relative abundance was less than one-third 

 of that in the first test. 



6. Liquefiers did not occur in so great numbers as in the 

 other experiments. While there was moderate increase in 

 total numbers, there was a decrease in percentage, and at the 

 end they formed a much smaller proportion of the total num- 

 bers than at the beginning. 



7. There were about four miscellaneous types of bacteria 

 which, as in the other cases, were present in small numbers in 

 the first one or two plates and disappeared so as not to be de- 

 tected in the later tests. 



8. The total number of miscellaneous species was somewhat 

 larger in this experiment than in the other two. 



4 



