CHEMISTRY OF COWS' MILK 7 



point, there appears to be a tendency for milk to be- 

 come less rich in fat with each succeeding period of 

 lactation, especially after the second, though individ- 

 ual exceptions are not infrequent. More data are 

 needed to settle the question definitely. 



(4) Influence of advance of lactation on the fat 

 content of milk. In general, it is found that the per 

 cent, of fat in milk increases as the stage of lactation 

 advances after the third month, as illustrated by the 

 following data from the records of the New York 

 (Geneva) Station, covering 10 months from the time 

 of calving: 



NUMBER OF Per cent, of 



MONTH OF LACTATION fat IH milk 



I . 4-54 



2 4-33 



3 4-28 



4 439 



5 438 



6 453 



7 456 



8 . 466 



9 479 



10 5.00 



(5) Variation of time between milkings in rela- 

 tion to the fat content of milk. As a rule, the longer 

 the time between two successive milkings, the smaller 

 is the per cent, of fat in the milk ; and the shorter the 

 time between milkings, the greater the per cent, of fat. 

 When the time between milkings is uniformly equal, 

 the variation of fat in milk is small, provided the gen- 

 eral environment of the animal is the same. How- 

 ever, as there are not commonly such entirely uniform 



