2 MilJc and Its Products. 



or lobe is furnished with a single opening connect- 

 ing with a single duct, in others several ducts 

 open independently upon the surface of a single 

 nipple or teat. The mammary gland is a true 

 organ of secretion in the sense that its product (milk) 

 contains substances not before existing in the blood, 

 that are formed during the process of secretion in the 

 gland itself. In the cow the mammarj^ glands are lo- 

 cated on the posterior portion of the abdomen be- 

 tween the hind legs, and each gland is made up of 

 two lobes or quarters, each having a single outlet 

 furnished with a single duct, though there are often 

 one and sometimes two rudimentary ducts upon the 

 rear quarters, and which are occasionally developed to 

 such an extent that milk may be drawn from them 

 in small quantities. The whole organ is spoken of as 

 the udder, and the ducts as teats. While the mam- 

 mary gland is essentially a female organ, it is present 

 in a rudimentary condition in the males of all mam- 

 rnals, and in exceptional cases in man and in the lower 

 animals the organs of males have developed to such a 

 degree as to secrete milk. 



The cotv^s udder. — The udder is enclosed in a fold 

 of skin, which is here thinner and softer than upon 

 other parts of the body, and is supported by a band 

 of fibrous tissue that springs from the median line of 

 the body and extends through the whole substance of 

 the gland. It varies very much in size and shape 

 in different animals and in the same animal at dif- 

 ferent times. Its size is not always an indication 

 of the secreting powers of an animal, since the num- 



