GROWTH OF BACTERIA IN NORMAL IMILK. 3 1 



Experiment No. i. Novcmbei'. — The milk in this and all 

 other experiments of this section was taken from a single cow 

 at the barn of the Connecticut Industrial School for Girls in 

 the vicinity of Middletown. It was taken at once to the lab- 

 oratory and the first set of plates made from it while the milk 

 was still warm; it was then kept at 20° C. and other plates 

 were made at intervals of about six hours until the milk was 

 twent5'-four hours old. The results are shown in Tables i 

 and 2 on page 30. 



The study of the figures given in these tables shows the fol- 

 lowing salient facts: 



1. During the first six hours there was no change in the 

 number of bacteria in the milk and practically no change in 

 the varieties found. The slight differences in numbers and 

 percentages given in the table are possibly only errors in the 

 method, although they may indicate an actual change in the 

 relative number of the different species of bacteria. 



2. From the beginning of the experiment to the close there 

 was a constant increase in the number of B. aeidi lactici. This 

 was an increase not only in actual numbers, but also in per- 

 centage, the milk at twenty-four hours old showing 61 per 

 cent, of this species. 



3. B. acidi lactici II. was not found on the plates. 



4. B. aerogenes played no considerable part in this experi- 

 ment. It was not found in the earlier tests and appeared only 

 in the last two. 



5. The Streptococcus shown in the fourth column existed in 

 very great numbers at first and continued to increase in num- 

 bers through the series of tests. The percentage, however, as 

 shown by Table 2, underwent a tolerably constant decline, and 

 was at the close only half as great as at the beginning. 



■ 6. The two species of Sarcina were present in moderate 

 numbers throughout the whole series; they increased slowl}" in 

 actual numbers but there was a decline in relative abundance. 



