COMPOSITION OF MILK AND CREAM 49 



canal or opening in the centre of each teat. There are therefore 

 four milk cisterns in the udder, one for each teat. It is probable 

 that when the udder has become accustomed to hold in its ducts and 

 cisterns a certain quantity of milk it will for a time secrete nearly 

 the same amount during each interval between milkings. After a 

 while, however — if the cow is milked more frequentlv than usual — 

 the udder will not continue to secrete the same amount of milk and 

 the exceptional quantity obtained by frequent milkings will cease. 

 Milking three times daily is practiced in some parts of Europe, but 

 milking more than twice in the twenty-four hours is rarely con- 

 sidered economical in the United States, and is not done except in 

 the case of very heavy milkers or in cows newly calved. 



Milk is formed continuously all the time and not chiefly at 

 milking time, as has been thought. 



Milking at the same hours twice daily, as at five a.m. and five 

 p.m., gives the same amount of milk at each milking. Milking has 

 no effect on milk formation. Frequent milking increases the milk- 

 yield simply by more complete emptying of the udder. The 

 longer the interval between milking the larger the quantity of 

 milk and the poorer the quality of the milk; the shorter the- 

 interval, the smaller and richer the yield of milk. In the summer 

 the nights are short and therefore the morning milking is apt to 

 be richer. In winter the reverse is true and the night milking is 

 likely to be the richer. 



The following analyses of the milk of one herd at the Delaware 

 Experiment Station show this : 



Night Milk Morning Milk. 



Per Cent. Fat. Per Cent. Pat. 



July 24th 3.76 4.67 



February 5th 4.56 3.53 



The season of the year influences the composition of milk. 

 In the summer the percentage of fat and other solids is lowest. In 

 the winter months the milk is richest in fat and solids not fat. 



