2 Milk 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 mammary glands are lo- 
eated 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 
reav quarters, and which are occasionally developed to 
such an extent that milk may he 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- 
mals, 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 cow'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- 
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