CHAPTER II. 

 MILK SECRETION. 



The Mammary Gland as a Secretory Organ. — The mam- 

 mary gland of females belonging to the order of mammalia, 

 secretes a fluid known as milk. This substance is strictly a 

 secretory product. There are two kinds of glands present 

 in the animal body; viz., the excretory and the secretory. Gen- 

 erally speaking, an excretory gland is one which receives or 

 absorbs the waste matter of the body, and causes it to be 

 carried off without causing any marked change to take place 

 in the substance excreted. A secretory gland is one in which 

 the raw material is obtained from the blood and then manu- 

 factured into a special different product within the gland 

 itself. As an example of a secretory gland, the milk-gland 

 of the cow's udder is an apt illustration. The glands in the 

 mouth secreting saliva, and those in the walls of the stomach 

 secreting the digestive fluids, are also secretory glands. 



Internal Structure of Cow's Udder. — The cow's udder is 

 composed of two separate glands, the right and left halves. 

 These two glands are distinctly separated from each other 

 by a fibrous tissue running longitudinally. This fibrous par- 

 tition extends along the abdomen in front, and back to a point 

 between the thighs of the cow. It also serves to hold the 

 cow's udder in place. There is no connection at all between 

 the right and left gland, and consequently milk cannot be 

 drawn from the left side over to the right, and vice versa. 



Each of these right and left halves is again divided into 

 two parts, thus making the cow's udder appear in quarters. 

 The cow's udder may then be said to consist of two glands 



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