i] STRUCTURE OF THE COW'S UDDER 5 



the cells possess a granular appearance, and the 

 central cavity above referred to is small ; but during 

 the process of secretion the cavity becomes dilated. 



The teats consist of two parts : the upper part, 

 which is known as the basis, and the lower, which is 

 known as the nipple. The nipple of the teat con- 



FIG. 4. A portion of the mammary gland, magnified about 400 diameters, 

 showing one complete and two incomplete alveoli, a, a, a, Short, columnar 

 epithelial cells lining the alveolus, each having an oval or rounded nucleus ; 

 b, I, 5, epithelial cells containing next the interior of the alveolus a milk 

 globule ; c, c, c, milk globules which have been set free from epithelial cells. 



tains numerous blood-vessels, and has at the base 

 muscular fibres (see Frontispiece). 



It has been calculated that the two milk-glands 

 and the four milk- cisterns in the udder of an average 

 milk cow, when the udder is not in any way dis- 

 tended, that is, as it would be after the cow has been 

 milked, have a cubic capacity of from 10J to 11 J 

 pints. 



