26 STORRS AGRICULTURAL EXPERIMENT STATION. 



while the bacteria were fewer than 10,000,000 per cubic centi- 

 meter, was of more significance than the study of the same 

 problem in later hours. Moreover, in a previously published 

 work* we have shown that, in cream, in the later hours the 

 development of the bacteria is always of the same general char- 

 acter. It has been there shown that the development of the 

 bacteria in the period of ripening always results in the disap- 

 pearance of most of the miscellaneous bacteria and the exces- 

 sive multiplication of two or three .species of lactic bacteria. 

 In some of the experiments reported later in the present article 

 it will be seen that these same facts were demonstrated to be 

 true of milk which had been kept more than twenty-four 

 hours. The first twenty-four hours, therefore, are those in 

 which the numerous species of bacteria in milk may be ex- 

 pected to develop or decline. These considerations together 

 have convinced us that the most useful foundation for a study 

 of the growth of different species of bacteria in milk is the 

 careful analysis of the development of bacteria during the first 

 twenty-four hours. In this series of experiments, therefore, 

 the analyses extended over a period of only about twenty- 

 hours, the tests being made at intervals of about six hours, 

 with slight variations to suit convenience. 



The results obtained in the experiments are given in the 

 tables on the following pages. Tfiere are two tables for each 

 experiment, which may be explained as follows: 



In the first table the first column gives the number of hours 

 after milking at which the different sets of plates were made. 

 The second column gives in round numbers the total number 

 of bacteria per cubic centimeter in the milk at the different 

 periods. Each succeeding column gives the number of a par- 

 ticular species or group of bacteria capable of differentiation 

 upon the litmus gelatin plates. A dash inserted in the column 

 indicates that none of the colonies of that species were dis- 

 covered on the plates; an interrogation point signifies that the 

 number of bacteiria was so small as not to be included in the 

 count, although not entirely absent from the sample of milk. 



In any period the sum of the numbers given in the different 

 columns .should in reality be equal to the total number given in 

 the second column; as a matter of fact, however, discrepancies 



* Storrs Expt. Sta. Rept., 1900. 



