CHAPTER XL 

 COMPOSITION AND QUALITIES OF MILK 



Milk is a white liquid with a yellowish tinge. It is secreted 

 from the blood by two large glands. These glands lie outside 

 the body walls, being covered by the skin, and form the vdder. 

 Each gland has two sections or quarters. From each section 

 there is a tube or duct through which the milk is drawn. 

 This duct is enclosed by fleshy walls and is called the teat. 

 At the top of each teat there is a small cavity capable of hold- 

 ing from one-half pint to a pint of milk. This cavity is called 

 the milk cistern. Leading into this cistern are ducts from 

 other parts of the gland. These ducts have their origin in small 

 clusters of cells where the milk is secreted. There is a net- 

 work of blood vessels extending throughout every part of the 

 gland. The glands on the right and left sides of the udder 

 have no connection whatever, and there is very little connec- 

 tion between the front and hind quarters of either half. 



The udder contains very little milk at any one time. Most 

 of the milk is secreted while the milking is being done. Just 

 how this secretion takes place is not well understood, but we 

 know that milk is a true secretion, because the elements which 

 it contains are different from the elements found in the blood. 

 The milk is kept from leaking out of the udder by a little 

 muscle which draws the opening at the end of the teat tight 

 shut. This muscle is called a sphincter muscle. Occasionally 



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