MILK. 



679 



body, but there is underlying it a strong layer of connective tissue, 

 from which elastic. fibers ramify in the substance of the glands, and 

 serve to give t,he parts solidity. Ligaments connect the upper part 

 of the glands with the muscles of the belly^ The fibrous partition 

 is the most important to hold the mammary glands in position. 

 Each of the mammary glands when deprived of its natural cover- 

 ings, represents a grayish-red substance of 9 to 20 inches long, 6 to 

 12 inches deep, and 4 to 8 inches broad in the period of milking. 



Fig. 839 gives a view of the appearance of .the udder of a cow, 

 denuded of the skin. 



The secretion of milk is generally possible when the heifer is 

 two years old ; but when the udder is irritated, milk may be given 

 during the first year. 



The interior of a cow's 

 udder is composed of a 

 marvelous ramification of 

 ligaments and tissue, 

 which, interlacing each 

 other, support the udder in 

 position. Blood veins, milk 

 ducts, cavities, glandules, 

 lobules, and vesicles are 

 distributed throughout 

 the udder ; and in Fig. 840 

 we give an illustration of 

 ' the net-work interwoven 

 in the milk glands of this 

 wonderful system. If a pliable probe be passed up the inside of 

 the teat, it will traverse a duct, which opens into a reservoir com- 

 municating with other reservoirs or with ducts ; and following one 

 or other of these ducts, the pVobe finally comes to a small saccular 

 cavity, and stops. Within this cavity and its vesicles and cells the 

 fats of milk are produced, and there are numbers of similar cavities. 



The interplacihg of the main ducts and the lobules is shown in 

 Fig. 841. A microscopical examination will reveal that these cavi^ 

 ties, or lobules, themselves irregular in size and shape, are composed 

 of vesicles which also vary in the same particulars. 



One of the lobules is shown in Fig. 842. It consists of sixteen 

 vesicles, indicated in the figure, and the cells which the vesicles 

 'contain, wonderfully minute and delicate, are also shown. 



The fat of the cow is constantly supplied to these cells, which 

 throw it off in the form of cream globules. These globules, when 



Fie. 842.— Lobule of Milk Gland. 



