GROWTH OF BACTERIA IN NORMAL MILK. 39 



Experiment No. /. November. This experiment was per- 

 formed under conditions identical with those of the other three. 

 The results are shown in Tables 7 and 8. 



The significant facts shown by this experiment are as fol- 

 lows: 



1 . The usual increase in total number of bacteria and in 

 total number of each of the common species of micro-organism 

 is seen. As in the other cases the few species of miscellaneous 

 bacteria, present at the outset in small numbers, failed to in- 

 crease and disappeared in the later tests of the experiment. 



2. A study of the table of percentages shows certain irregu- 

 larities from those of the other experiments. There fails to be 

 a regular increase in the proportion of B. acidi lactici. The 

 Streptococcus group also shows irregularities. The third and 

 fourth tests indicate a smaller number of this group than the 

 second and fifth. The explanation of this is beyond doubt 

 given in the column of liquefiers, for it will be seen that the 

 proportion of these organisms in this milk was excessively 

 high, in the third and fourth test reaching 50 and 47 per cent. 

 This high percentage of liquefiers made it impossible to keep 

 these particular plates until the B. acidi lactici and the Strepto- 

 coccus groups were properly differentiated, and the estimates of 

 these two species upon the third and fourth plates are, therefore, 

 quite unreliable. The same statement must be made in regard 

 to the two species of Sarcina, which in young plates are not 

 easily differentiated from B. acidi lactici or the Streptococcus 

 group. As a consequence the numbers given of these three 

 species in these two tests are not satisfactory. 



