23 CHAPTER XIII. 



SKIN AND ITS APPENDAGES. 



Skin. Palmar surface of human finger, (p. 11, s. 22 & 24, 

 c. P., m. B.) 



(L) The epidermis has already been described. (See stratified 

 epithelium.) 



The dermis or true skin consists of fibrous tissue of con- 

 siderable density near the surface, but looser deeper down, 

 where also are masses of sub-cutaneous fat (paniculus adeposus). 



The papillae are buried in the epidermis and contain vascular 

 loops or nerve endings (touch corpuscles) sometimes in the 

 same papilla, but usually in separate ones. These corpuscles 

 are masses of an ovoid shape consisting of spirally wound fibrous 

 tissue in which a nerve may be seen to end. The sweat glands 

 are simple tubes, the secreting portions of which lie deep in the 

 dermis, where each forms a convoluted mass. From these the 

 duct runs to the surface, passing through the epidermis in 

 a spiral course. Find on a level with the fat the paccinian 

 bodies. In structure they are concentrically laminated around 

 the nerve, of which they form the terminal coverings. Here 

 find, also, small arteries and nerve bundles. (H) Examine 

 the structure of the touch corpuscles. The secreting part 

 of the sweat glands in T.S. shows externally a hyaline mem- 

 brane, next to this a layer of longitudinally disposed non- 

 striped muscle, and innermost of all secreting epithelium. 

 The ducts are lined by low cubial cells for which the 

 squamous variety is substituted in the epidermis. 



