GROWTH OF BACTERIA IN NORMAL MILK. 4 1 



Experiment No. 5. December. The milk in this experi- 

 ment was obtained from a different cow from that of the other 

 experiments, but from the same stable. In other respects the 

 conditions were identical. The results are showm in Tables 9 

 and 10. 



From these tables the following facts may be noticed: 



1 . There is a constant increase in the numbers of B. acidi 

 lactici, both in total numbers and in percentage. They did not, 

 however, reach a very high percentage in any of the experi- 

 ments. It will be noticed that the 30.9 per cent, given in the 

 fourteen hour test was anomalous. This is doubtless an error 

 introduced by the liquefiers, as mentioned below\ 



2. The other two common acid bacteria did not appear in 

 this sample of milk, with the exception of a small number of 

 B. aerogenes found in the last plate. 



3. The Streptococacs group was abundant and increased in 

 total numbers regularly through the whole series of experi- 

 ments, though the percentage remained practically constant. 



4. The total number of the two Sarcina species underwent 

 a constant increase, but there was a decrease in percentage, so 

 that in the last tests they had become a very small fraction of 

 the whole, less than 2 per cent. 



5. The most peculiar feature of this sample of milk was the 

 excessive number of liquefiers, which was greater than in any 

 other test we have made. Moreover, they continued to increase 

 until almost the very end, rising in proportion from 23.5 to 60.9 

 per cent, at the end of twenty hours, and then falling to 50 per 

 cent, at the end of twenty-four hours. This large number of 

 liquefiers made the differentiation of the acid organisms and 

 the Streptococcus group difficult and unsatisfactory, and it is 

 quite probable that the numbers given in the second and fourth 

 columns are in this case not reliable. 



6. There were only two species of miscellaneous bacteria 

 present in this sample. They were few in number and they 

 disappeared totally from the plates in the later tests. 



