8 QUESTIONS AND ANSWERS 



mass, which is more or less grayish red in color, 

 according to its varied structure, is covered on the 

 outside by a heavy fold of skin which is covered 

 with fine hair and has marked elasticity. 



Internally the udder is divided into four quar- 

 ters, the two quarters on the same side communi- 

 cating with each other and each quarter being sup- 

 plied with an outlet or teat. 



At the upper end of each teat is a fairly large 

 cavity called a milk cistern, each of which may hold 

 as much as one-half pint. In these the milk col- 

 lects after being secreted and carried from the 

 glandular cells by a more or less complicated series 

 of milk ducts and canals. At the lower end of 

 each teat a circular muscle exists, which, when con- 

 tracted, has the power of closing the lower opening 

 and preventing the escape of milk. 



Considerable muscular tissue exists in the udder, 

 especially around the walls of milk ducts and their 

 dividing points. These muscles are well supplied 

 with nerves so that the animal can by her will 

 power control to a considerable extent, for a short 

 time, the evacuation of milk after it has been 

 secreted by the small cells. She cannot, however, 

 control the actual secreting process. The milk- 

 producing power of an udder depends largely upon 

 the amount of blood carried to and from it through 

 the arteries and veins. 



How and from what is milk secreted? 



Milk is secreted from the blood while it passes 

 through the smallest blood vessels in the udder 

 called the capillaries and from the lymph while it 

 passes through the lymphatics. 



