374 



THE ESSENTIALS OF AGRICULTURE 



MP 



The milk sugar is a source of energy to the young animals, 

 and when extracted from milk is of value in feeding infants and 

 in diluting strong drugs. Nowhere else in nature is this kind 

 of sugar formed, and it is the most readily digested form of 

 sugar for infants. The ash of milk furnishes the ash of the 



body and is used prin- 

 cipally in the growth 

 of the skeleton. 



488. Bacteria in milk. 

 All milk drawn in the 

 ordinary manner con- 

 tains bacteria, most of 

 which get into the milk 

 after it is drawn. The 

 most important are the 

 lactic-acid bacteria, or 

 those which cause milk 

 to sour by changing 

 the milk sugar into 

 lactic acid. Other bac- 

 teria, some of which 

 cause bad flavors and 

 odors, also get into the 

 milk. To check the 

 souring process one 

 must check the growth 

 of the bacteria that get 

 into the milk. To do 

 this, the milk must be 

 drawn in a covered pail 

 (Fig. 187), and as soon as it is drawn it should be cooled and 

 kept clean and cold. The lactic-acid bacteria grow best when 

 the milk is kept at a temperature above 70 degrees ; therefore 

 the milk should be cooled and kept at 50 degrees or even 

 a lower temperature, and should be cooled as soon as possible 

 after milking. 



FIG. 186. Butter-fat globules 



Reading from above downward, samples are shown 



of cream, milk, and skimmed milk under the same 



magnification. Proportionate numbers of fat globules 



are shown 



