DAIRY MEETING. l8l 



Next take the matter of cold. Bacteria, both of the disease 

 and acid producing species, grow best at the temperature of the 

 body. Any lowering of the temperature below this point retards 

 their growth, and the more the temperature is lowered the more 

 is bacterial growth retarded. A temperature of 50° F. retards 

 their growth considerably. Below 40° F. the growth is slight, and 

 at a freezing temperature bacterial growth stops. Thus a frozen 

 milk can be kept sweet indefinitely. If, then, we cool the milk 

 at once after milking to a temperature below 50° F. we shall be 

 able to hold off the souring of the milk for a long time, since we 

 are preventing the rapid growth of the germs that produce this 

 sourness. It has often been noticed that morning's milk will 

 sour quicker than will the milk of the night before, which has to 

 wait until after the morning milking for delivery. We here 

 have the effect of cold on the souring of milk well illustrated, 

 for the night's milk is usually put in a spring, or well, or in a 

 cool cellar until morning, and the cold there met with very 

 greatly retards the bacterial growth. But the morning's milk 

 is at once put into cans for delivery without any preliminary 

 cooling. Here in the fresh and warm milk the bacterial growth 

 soon exceeds that in the older but cold milk of the night before. 

 The result is a quicker souring of the fresher milk, as it offers 

 greater chances for rapid growth of the bacteria that cause 

 this souring. Thus a dirty milk cooled as soon as milked and 

 kept cool will remain sweet longer than a clean milk that has 

 been allowed to stay warm; but it must be remembered that, 

 while retarding their growth, cold does not kill either the acid- 

 producing or the disease-producing bacteria, so that it can 

 never take the place of cleanliness in the production of a sani- 

 tary milk. The bacteria in the cold milk simply have their 

 power of reproduction curtailed. They still retain the power 

 of resuming this function when temperature conditions become 

 favorable. Thus cold really comes second to cleanliness, and 

 not in the place I have taken it up for the sake of convenience. 



We now come to the question of cleanliness in the production 

 of milk. This feature of the question deals not with the keep- 

 mg down of bacterial growth, but in preventing entrance of 

 bacteria into the milk to cause the trouble that makes their later 

 control necessary. Much has been written on this subject and, 

 if the various recommendations of investigators could be car- 



