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EXPLANATION OF EXERCISE XX 



In sanitary milk production it must be kept constantly in mind 

 that clean milk means a product reasonably free from germ life. It 

 is not as difficult to keep germs out of milk as is commonly supposed. 

 There are a few simple and inexpensive practices which if carefully 

 followed will do much in aiding the dairyman to produce a good 

 product. 



It is the purpose of the following experiments to illustrate the value 

 of certain dairy practices in clean milk production and the harmful 

 effects of certain other practices in producing clean milk. 



In performing these experiments it must be borne in mind that 

 anything which prevents the entrance of dust and dirt into milk 

 is an aid to clean milk production. On the other hand, any disturb- 

 ance which causes dust particles to float around in the air makes it 

 easily possible for these particles to enter the milk while it is being 

 drawn and so contaminate it. 



The use of the small top pail, and wiping the udder with a damp 

 cloth just before milking, are two things which are easy to do and are 

 comparatively inexpensive. At the same time, they are exceedingly 

 helpful in keeping germs out of milk. 



On the other hand, the practice of feeding hay or grain just before 

 milking stirs up a dust and therefore makes it possible for a larger 

 number of micro-organisms to enter the milk. 



EXERCISE XX 

 THE VALUE OF THE SMALL TOP PAIL IN CLEAN MILK PRODUCTION 



1 . Carefully sterilize an ordinary wide top milk pail and a small 

 top or covered milk pail. 



2. Select two cows standing near one another and whose flanks 

 and udders are alike as regards the amount of visible dirt on them. 

 Milk one cow in the wide mouth pail and the other cow in the small 

 top or covered pail. 



3. Take a sample of milk in a sterile bottle from each pail and 

 plate the samples for bacteria. If it is necessary to hold the samples 

 for any length of time before plating, the bottle should be set on ice. 



4. After the colonies in the plates have developed, note if there 

 is any difference in bacterial content of the milk drawn in the wide 

 mouth pail and that drawn in the small top or covered pail. 



