GROWTH OF BACTERIA IN NORMAL MILK. 55 



From these tables the following detailed points may be 

 noticed: 



1. The preliminary icing of the milk for fourteen hours did 

 not in this case produce a reduction in the number of bacteria 

 as it did in the previous experiment. There was, at the end 

 of the icing, an increase from 23,000 to 78,000. 



2. It was found, however, that the number of bacteria de- 

 veloping in the iced milk never became as great, even at the 

 time of curdling, as in the non-iced milk. The non-iced milk 

 at the time of curdling contained nearly twice as many bacteria 

 (1,200,000,000) as the iced milk (692,000,000). There was 

 also a greater rapidity of multiplication of bacteria in the milk 

 which had not been iced. 



3. The variet}^ of bacteria found in the iced milk was 

 greater than that present in the milk that had not been iced. 



4. This sample of milk contained at the outset apparently 

 no representative of B. acidi ladici II. They made their ap- 

 pearance in the later stages and were found in both the iced 

 and the non-iced milk. 



5. The Streptococcus group was present in considerable num- 

 bers, and underwent an increase, in actual numbers and per- 

 centage, and a subsequent decrease. In this experiment, as 

 in the last, this species decreased much more rapidly in milk 

 that had not been iced. In the iced milk the percentage was 

 at first almost 32, rose to 56, and then became reduced to 15 

 per cent. In non-iced milk the percentage decreased rapidly, 

 so that at the close of the experiment there was less than .5 per 

 cent, of this species of bacteria found, the total number being 

 also less than in iced milk. 



6. In this experiment the effect of icing seemed to be to 

 increase the development of liquefying bacteria. The propor- 

 tion of liquefiers in the iced milk rose to 37 per cent, and then 

 dropped off rapidly. In the non-iced milk the percentage in- 

 creased slightly and dropped off more rapidly, and at the end 

 the liquefiers were much less abundant than in the iced milk. 



7. In both samples of milk five of the varieties of bacteria, 

 namely, the two Sarcina types and the species numbered 220, a 

 and e, completely disappeared in the later tests. This of course 



