THE FEEDING OF MILCH CATTLE 311 



(c) The age of the cow. 



The general capacity of the more highly developed 

 animals increases during the first period of life, then 

 remains for some time at the same level and after- 

 wards begins to diminish. It is the same with the 

 milking capacity of cows, and observations have 

 shown that the yield of milk increases up to about 

 the time of the fifth or sixth calf, whereas the 

 average percentage of fat in the milk remains con- 

 stant up to that time and for several years longer. 

 Great differences are shown though in the behaviour 

 of individual cows. 



(3) The influence of other factors on the formation of 

 milk. 



(a) The frequency and manner of milking. 



There can be no doubt that the passage of the 

 milk from the alveoli to the milk cistern is easiest 

 and most rapid when the udder is empty. When 

 the udder is more or less filled there is a damming 

 of the small ducts leading from the alveoli, and the 

 pressure acting upon the alveoli hinders the separa- 

 tion of milk. From this it would be thought that 

 more frequent milking would increase the yield of 

 milk, but there are other factors to be considered. 

 Many circumstances point to a considerable portion 

 of the milk only being formed in the alveoli under 

 the stimulus of milking. It has been computed 



