24 



BULLETIN OF 



Massachusetts Boaed of Agriculture. 



MILK AND CREAM. 



By J. B. LiNDSET, Ph.D., Department of Foods and Feeding, Hatch Experiment 

 Station of the Massachusetts Agricultural College. 



General Structure of the Udder of the Cow. 



The udder of the cow consists of two milk glands, a left and right, 

 separated from each other by a fibrous tissue (ligamentum suspensorium 

 mamarum). This tissue layer, or wall of division, is connected by elas- 

 tic muscles with the connective tissue which surrounds the glands, and 

 also with the muscles of the belly, thus holding the milk glands in posi- 

 tion. 



The two milk glands are each of a reddish gray color, and consist, 

 properly speaking, of a glandular structure known as the gland basket. 

 In case of ordinary mature milch cows, each gland is about (S\ inches in 

 depth and \2\ inches in length. The glandular mass may be divided 

 into lobes, lobules and alveoli. Plumb makes this clear by likening the 

 lobe to a bunch of grapes, the lobules to ^ single grape and the alveoli 

 to smaller divisions within the single grape. The lobules of the gland 

 are surrounded by a fully developed net-work of capillary vessels, in 

 which the materials for the formation of the milk circulate through the 

 numerous lymph tracts The alveoli are microscopic terminations of 

 extremely fine canals. They are covered externally with a structure- 

 less membrane, and internally are lined with a continuous single layer 

 of epithelial cells These cells have a diameter of .04 of a millimeter. 

 When the cow is in milk they are swollen and protrude into the alveolian 

 cavity. The microscopic canals, of which the alveoli are the enlarge- 

 ments, unite together among themselves into ever widening ducts — the 

 milk ducts — and end eventually in large, hollow cavities, the so-called 

 milk cisterns or reservoirs. 



These cisterns, four in number, situated above each teat, extend up- 

 wards into the gland and downwards almost to the end of the teat. The 

 teats, two for each milk gland, are encircled at the lower end with 

 numerous fibers, forming the sphincter muscle, which prevents the 

 escape of the milk under ordinary conditions. 



The individual lobules are enveloped in connective tissues, which 

 unite them in a glandular mass, and this connective tissue is in turn 

 covered with adipose tissue, and the whole udder is enveloped by the 

 skin. 



