ELEVENTH LECTURE. 



THE SKIN. 



648. The skin (Plate XXXVII. , 10) is a dense, porous, and very 

 sensitive structure, serving to cover and protect the body from external 

 injury. It is composed of two layers : — 



ist. — External— The Cuticle, or Epidermis. 

 2nd. — Internal — The Dermis, True Skin, or Cutis 

 Vera. 



The skin varies in thickness in different parts of the body. It is fine 

 and soft where much motion is required, and dense and thick where 

 the parts are exposed — as the back, shoulders, &c. 



649. The Cuticle, or Epidermis, is composed principally of scales, 

 which are cast off when done with, like the scales from the body of a 

 lish. It is non-sensitive. The deepest part of the epidermis is known 

 as the Rete Mucosum, and it is to it that the skin owes its colour. 



650. The Cutis Vera, dermis, or true skin, contains the sebaceous, 

 fat, or oil glands, the sudoriparous or sweat glands, the hair, 

 and hair follicles. 



651. The Sebaceous Glands (Plate XXXVIL, 10, E.) secrete an 

 oil which pours into the hair follicles, for the purpose of lubricating 

 the skin, and keeping it and the hair soft. 



652. Sudoriparous or Sweat Glands (Plate XXXVIL, 10, B.).— 

 It is said that there are about 2,000 pores in one square inch of skin, 

 for the purpose of perspiration, an action which is both insensible and 

 sensible. The quantity of sweat varies very much, according to the 



