VARIATIONS OF MILK CONSTITUENTS 169 



the necessity for dairymen to guard against the 

 effects of drouth by making provision for furnish- 

 ing some form of succulent food then. At such 

 times, there is an enormous loss due to shrinkage 

 in yield of milk; and, in cheese-making, there is an 

 abnormal loss of fat in whey, resulting in decreased 

 yield of cheese for 100 pounds of milk. 



THE RELATION OF FAT AND CASEIN IN 

 CHEESE-FACTORY MILK 



We have seen that the relation of fat and casein 

 is a variable one, the variations being less wide, of 

 course, in the case of herd milk than in that of 

 individual cows, and especially of single milkings 

 of individuals. But, in the case of averages of 

 several analyses of milk -and in the case of milk 

 of herds, especially when cows are of one general 

 type in respect to breed, a certain degree of uniform- 

 ity exists in the relation of fat to casein. In New 

 York a careful study was made of the milk of each 

 of 50 different herds of cheese-factory cows during 

 one season (May to October), and, as one of the 

 results, a general relation was noticed between the 

 fat and casein. In general, it was found that when 

 the fat in milk increases i.o per cent, there is an 

 average increase of casein amounting to 0.4 per 

 cent. This was found to hold quite satisfactorily 

 when applied in case of ordinary herd milk varying 

 in fat content from 3 to 4.5 per cent and, in many 

 cases, outside of these limits. In milk containing 

 less than 3 per cent of fat, the casein content is 

 usually higher in relation to fat than in milk with 

 more than 3 per cent of fat; while, in the case of 



