GENERAL STRUCTURE. 19 
tive and genital tracts, the epithelium changes to a soft 
delicate nature, and is then known throughout these pas- 
sages as mucous membrane. 
The coriuwm or dermis is a form of fibrous connective 
tissue whose deepest portion forms the white fluffy areolar 
substance cut in removing the skin. In many regions just 
below the true skin is a layer of adipose tissue, which when 
examined under the microscope is seen to be composed of 
numerous globular fat-cells supported by fibrous areolar 
tissue. The seven pads on the forepaw and the five on the 
hind one consist of greatly thickened epidermis, the corium, 
and masses of fibrous connective tissue enveloping many 
fat-cells. 
The sebaceous or oil glands lie in the corium, and by 
means of a duct open into the hair follicle near the sur- 
face. The sudoriparous or sweat glands, composed of 
coiled tubes, are present in the subcutaneous tissue, from 
whence a duct extends to the surface. Although there are 
no blood-vessels in the epidermis, numerous nerve termina- 
tions are present in the deeper portions. The true skin is 
richly supplied with both nerves and blood-vessels. 
The claws produced by a special modification of the 
epidermis are among the most important appendages of the 
skin. Five of these are present on each forefoot, while only 
four occur on the hind one. At the root of each claw, 
the dermis forms a crescentic fold over it, and beneath is a 
number of papillz richly supplied with blood-vessels. This 
entire structure forms the matrix of the claw, which is set 
around the terminal part of the distal phalanx of each digit. 
Claws, or some similar structures, such as nails or hoofs, 
are present in all mammals except the Cetacea. 
Another important appendage of the skin is the hair, 
which covers the entire body except the tip of the nose and 
the pads of the feet. Its length and color vary with the 
