RELATION OF BACTERIA TO THE DAIRY. 185 



stimulates bacterial growth to a maximum. If allowed to re- 

 main warm until it cools naturally, this will take so long, 

 especially in warm weather, that the bacteria will become very 

 numerous within a short time. 



The milk dealer is sometimes puzzled by the fact that morn- 

 ing's milk will sour more quickly, after delivery to the cus- 

 tomer, than will the milk of the night before, though the latter 

 is actually twelve hours older. The explanation of the fact 

 is simple enough. The night's milking is to be delivered in 

 the morning and, meantime, is placed in a cool spring or ice 

 chest, and its temperature consequently rapidly lowered. The 

 bacteria growth is immediately checked. When taken for dis- 

 tribution the next morning it does not have many bacteria, and 

 it warms up so slowly that it is long before it is warm enough 

 for the bacteria to grow very rapidly. But the morning's milk 

 is taken directly from the cow, placed in the delivery cart and, 

 while still at a high temperature, is carried around for distribu- 

 tion. At this high temperature the bacteria multiply quickly, 

 and soon their number is higher than that in the night's milk 

 which has been cooled. The morning's milk actually sours 

 first, simply because it failed to receive the cooling immediately 

 after the milking. 



The remedy for this is, of course, a cooling of the milk im- 

 mediately after the milking ; hence the quicker the cooling and 

 the lower the temperature, the better. It is surely unneces- 

 sary to add that the milk should then be kept at as low a tem- 

 perature as possible until it is used. This fact is fully under- 

 stood by all who handle milk and the numerous devices for 

 the use of ice, in cars or in milk wagons, are testimonials to 

 the absolute necessity of low temperatures for the purpose of 

 preventing an undue growth of bacteria. 



From these facts it will be seen that it is impossible to make 

 any statement as to the proper number of bacteria to be found 

 in milk of any given age. The number is highly variable and 

 16 



