REDUCTION OF BACTERIAL CONTAMINATION. 55 



in this respect is, therefore, a source of bacterial contamina- 

 tion. If, however, this cooling is done, not in the barn but 

 in a clean dairy or a room that is kept clean, the .amount of 

 contamination that comes from the air during cooling is not 

 very great. That the milk should be cooled immediately is 

 beyond question, but it can be cooled just as efficiently, and 

 perhaps more satisfactorily, by being placed at once in 

 the sterilized bottles, immersed immediately in cold water 

 and kept there until it has had an opportunity to cool. 

 Those who have carefully used this method are convinced 

 that the results are fully as satisfactory as those obtained 

 by passing the milk over a cooler, which at the same time 

 aerates the milk. 



Many dairymen think it necessary to aerate the milk for 

 the purpose of getting rid of the so-called animal odors. 

 The milk, as drawn in an ordinary dairy, does have a certain 

 odor which is removed by the aeration. But these odors 

 are due in large degree, if not wholly, to the filth contamina- 

 tion of the milk. If the milk could be drawn directly from 

 the cow without becoming contaminated with the various 

 forms of filth already referred to, the animal odors would, 

 under ordinary circumstances, be slight if at all appreciable. 

 Such milk would not require any aeration. Dairymen 

 who are particularly careful in their dairies and give the 

 greatest attention to cleanliness are not troubled with animal 

 odors, and find that the immediate bottling of milk, without 

 aeration, and its rapid cooling in cold water gives the very 

 best results. In other words, the necessity of aeration will 

 be proportional to the amount of filth contamination of the 

 milk during the milking. The best kept dairy will feel the 

 need of aeration the least, while the poorly kept dairy feels 

 this need the most. But under any circumstances, whether 

 the milk is aerated or not, immediate cooling is an impor- 

 tant factor in the keeping power of the milk. 



