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 corium 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 papillae 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 



