328 MILK 



the temperature. Cooling facilities are not as efficient, as a rule, 

 as is desirable. The rate of multiplication of bacteria in milk, 

 according to Hunziker, is as follows : 



Original number of bacteria in the milk 5,000 per cubic centimeter 



After twenty-four hours at 42 F 2,400 " 



After twenty-four hours at 50 F 7,000 " 



After twenty-four hours at 65 F 280,000 " 



After twenty-four hours at 95 F 12,500,000 " 



The decrease at 5 C. may be explained by the so-called germi- 

 cidal property of fresh milk, which also may account for the rela- 

 tively small increase at 10 C. At higher temperature the influ- 

 ence of this property is of such short duration that the results are 

 not materially affected. 



Conn gives the following figures illustrating the multiplication 

 of bacteria according to temperature : 



NUMBER OF BACTERIA PER CUBIC CENTIMETER IN MILK KEPT AT DIFFERENT TEM- 

 PERATURES 



Conn further estimated that the initial number increased fivefold 

 at 10 C. during twenty-four hours and 750-fold at 21 C. (Fig. 161). 



a 



Fig. 161. a, Single cell. 6, Progeny of one cell, milk kept at 50 F. for 

 twenty-four hours, c, Progeny of one cell, milk kept at 70 F. for twenty- 

 four hours. (Conn, Storrs' Agric. Exp. Sta., Bull. No. 26, October, 1903.) 



The author concludes that "keeping of milk is more a matter 

 of temperature than of cleanliness/' and Harding says that "in 

 practically all cases when more than twelve hours elapse between 



