348 BOARD OF AGRICULTURE. [Pub. Doc. 



vious and even during milking these distended cells break, 

 and the milk thus distributed in the udder is drawn off by 

 the milker. The enlarged udder of the cow for a few hours 

 just previous to milking is not wholly due to the amount of 

 milk it contains, but rather to the distended or congested 

 condition of the glands. 



From the above brief outline of the several theories, it is 

 apparent that as yet we have but very little definite knowl- 

 edge of what actually takes place in the glands which results 

 in the production of the white fluid termed milk. It is 

 probable that the fat is derived to some extent from the fat 

 of the blood, but is formed largely as a result of cell activity, 

 and is, therefore, a secretion. The formation of milk sugar 

 and casein is still largely a matter of conjecture. 



It is evident, however, both from practical and scientific 

 observations, that the production of milk depends firstly upon 

 the large development and great activity of the milk glands, 

 and secondly upon the capacity of the animal to consume 

 and digest large amounts of food in order to supply these 

 glands with an abundance of the necessary raw materials. 



Properties of Milk.* 

 Milk in its normal condition is a pure, almost white fluid, 

 and perfectly opaque in large quantities. This lack of trans- 

 parency is due partly to the fat in suspension and partly to 

 a suspension of the nitrogenous and mineral matter. It has 

 a slight smell and a mild, rich, slightly sweetish taste. It 

 possesses a slight amphoteric (alkaline and acid) reaction, 

 due probably to the presence of alkaline carbonate and neu- 

 tral and acid phosphates. When allowed to stand for any 

 length of time, a multitude of minute fat globules rise to the 

 surface, and form a layer of cream. By continuous standing 

 milk coagulates. Coagulation can also be brought about by 

 the addition of small quantities of acid. 



The Ingredients or Milk. 

 The larger part of milk consists of water, which contains 

 a variety of substances in suspension and solution. The 



* In considering this subject it will be understood that cow's milk is always 

 meant, this being practically the only milk used in the United States. 



