THE GROWTH OF BACTERIA IN MILK 77 



bers of bacteria are due to the fact that the milk contains a 

 large amount of filth, with its special and injurious types of 



FIG. 36 GROWTH OF BACTERIA AT DIFFERENT 

 TEMPERATURES DURING 24 HOURS 



Each dot representing a single individual 



a. At 50 ... 7 bacteria 



b. At 70 . . . 700 bacteria 



bacteria. The bearing of this upon the question of municipal 

 examination will be considered later. 



The rapidity of growth of common bacteria at different tem- 

 peratures is graphically shown by the accompanying figure 36. 



THE GROWTH OF DIFFERENT SPECIES 



When drawn from the cow milk is at a temperature that 

 especially favors the development of most ordinary species of 

 bacteria. While different species differ somewhat as to the 

 temperature at which they grow best, a majority of them can 

 multiply most rapidly at about body heat, between 90 and 100. 

 Some species, however, find a lower temperature especially 

 favorable. Hence the kinds as well as the numbers of bacteria 

 in milk are largely affected by the temperature. 1 



At 33. If milk is frozen, bacteria do not grow at all. If it 

 is only a degree or two above freezing, they grow very slowly, 



1 Conn and Esten. Ann. Rep. Storrs. Exper. Sta., 1901. 

 Conn and Esten. Rev. Gen. d'Lait., i., p. 121, 1901. 



