76 STORRS AGRICULTURAL EXPERIMENT STATION. 



4. The growth which occurs after forty hours is due usually 

 to the Streptococcus group increasing in numbers, sometimes to 

 the B. acidi lactici II., and, in our experiments in one case 

 only, to the development of B. acidi lactici I. 



5. During the first forty hours there are slight fluctuations 

 in the species of bacteria which are found at different tests. 

 The Streptococcus group regularl}^ increases in total number 

 and percentage. I^iquefiers frequently increase. The Sarcina 

 species in one case increased slightly, but usuall}' remains about 

 constant, or sometimes decrease in numbers. The miscellane- 

 ous bacteria remain in about equal quantity throughout the 

 first forty hours. All of this simply means that for this period 

 there is ver}^ little change in the bacteria, but that the Strepto- 

 coccus appears to be able to grow at this temperature rather 

 more readily than the other species. 



6. In general it thus appears that a temperature of 13° 

 affects not onl}- the total numbers of bacteria but also the 

 species which develop. 



7. It appears that from a standpoint of the number of bac- 

 teria which are present in milk at any age, the question of 

 temperature is a factor of more significance than the question 

 of the original contamination. 



SUMMARY. 



// is well now to summarize briefly the general results which 

 have been obtained from the experiments described in the previous 

 pages. They are essentially as follows: 



1. There 7vas little regularity in the compa^-ative development 

 of the species present in milk. Numerous irregtilarities were ob- 

 served in different experi7nents zvhich are inexplicable by any data 

 as yet in our possession, and many differences i^i groivth were 

 found in different samples of milk kept binder apparently identi- 

 cal conditions. 



2. The number of bacteria which are present in fresh milk 

 gives no indication as to the number that may be present in later 

 hours. It frequently happens that milk which at the outset has 

 Sfnall numbers tvill in later hotirs have numbers cofisiderably 

 larger than those in other samples of milk 'which at the outset 

 co7itained more bacte?'ia, even though the two samples of milk are 

 kept under identical co7iditions. 



