XV. 



MILK AND MILK PKODUCTS 



329 



percentages of fat in the evening and morning milks that is affected, 

 rather than the actual difference between them. 



If cows could be milked at equal intervals of twelve hours, there 

 would probably be little difference, either in yield or in percentage 

 of fat, between the morning and evening product. Whenever the 

 exigencies of trade necessitate very unequal intervals, there is always 

 great risk of the milk taken after the long interval being deficient 

 ia fat 



By milking three cows four times a day, at intervals of six hours, 

 for four days and analysing the milk, the following average figures 

 were obtained : 



From these results it appears that the milk secreted between 5 a.m. 

 and 5 p.m. is much richer in fat but smaller in quantity than that 

 secreted at night, and that by far the largest amount is secreted in 

 the six hours after 11 p.m. 



But the results may be affected to some extent by the unequal in- 

 tervals, 15 hours and 9 hours, to which the cows had long been ac- 

 customed, having some influence upon their manner of secretion. 

 Other experiments have shown that cows, which have become habitu- 

 ated to a certain set of conditions, retain the same manner of secre- 

 tion for some time after the conditions have been changed. 



It is also well known that the milk first drawn from a cow at 

 milking time is very poor in fat (" fore milk "), while the last portion 

 (" strippings " or " afterings ") is very rich. Cases in which the 

 "fore milk" contains less than 0*5 per cent of fat have been noticed, 

 while " strippings " will sometimes contain as much as 10 per cent. 

 It is also found that the size, as well as the number of fat globules per 

 unit volume, increases as the milking proceeds. This is probably due 

 to a partial " creaming " taking place in the udder, since the produc- 

 tion of milk seems to be a continuous process. 



The writer has also noticed that, with many cows, the milk yielded 

 by the separate quarters of the udder differs very considerably, both 

 in fat content (which appears to be capricious in its distribution), and 

 also in solids-not-fat, and that it is the milk sugar which shows the 

 largest variation. 



For example, the following results were obtained with the evening 

 milk of one cow, the initial letters referring to the right fore -quarter, 



