BACTERIA COMMONLY FOUND IK COWS* MILK. 89 



The following instructive facts are shown from these 

 figures:* 1. At 15 0. (59 F.) there was no increase dur- 

 ing the first three hours, and during the first six hours only 

 an insignificant one. 2. At 25 C. (77 F.) the increase was 

 insignificant during the first three hours, but the number 

 of bacteria then increased rapidly at the temperature 

 so favorable to the growth of the bacteria. 3. At 35 0. 

 (95 F.) the development was rather rapid from the start, 

 but the increase in the bacterial content was still after 

 twenty-four hours not so large as at the last-mentioned 

 lower and evidently more favorable temperature. 



If a still lower temperature than 59 F. (15 0.) be used 

 for keeping the milk the bacterial growth is nearly com- 

 pletely checked. If the temperature of the milk is low- 

 ered to 45 F. (7 C.) immediately after the milking, the 

 bacterial content according to my results is practically 

 unchanged after twenty-four hours, and even after a still 

 longer time from what it was at the beginning of the cooling. 

 I have, however, observed in isolated cases that even at this 

 temperature a considerable increase has taken place ; this 

 increase always stopped entirely when the bacteria were 

 subjected to this temperature for 5-6 hours. The bacteria 

 able to multiply even at 45 F. (7 C.) thus appear to be 

 slowly paralyzed under the influence of this temperature. 

 Even when the milk has had a temperature of 43 F. 

 (6 0.), an increase of the bacteria has twice been found: 

 in the one instance the increase, strange to say, took 

 place a long time after the temperature of the milk had 

 been lowered to this point. The tenacious organisms 



* See also results obtained by Miquel, Ann. Microgr. 1889, Dec. 

 No. ; and by Baumann (Inaug. Dissert. Univ. KSnigsberg, 1893, pp. 

 16,17). W. 



