The Skin and the Kidneys 



185 



By the skin the body gets rid of a small quantity of salts, 

 a little carbon dioxide, and a large amount of water in the form 

 of perspiration. 



From the kidneys are eliminated nearly all the urea and 

 allied bodies, most of the salts, and a large amount of 

 water. Practically all the nitrogenous waste products leave 

 the body by the kidneys. 



278. The Skin as an Important and Complex Organ. 

 The skin is a blood-purifying organ as truly as are the lungs 

 and the kidneys, while it per- , 



forms other and complex duties. 

 It also serves as a protective 

 covering for the surface of the 

 body. 



The skin, being richly sup- 

 plied with nerves, is an impor- 

 tant organ of sensibility and 

 touch (sec. 370). 



The skin ranks as an impor- 

 tant organ of excretion, its prod- 

 uct being the sweat. 



The skin also plays an im- 

 portant part in regulating the 

 bodily temperature (sec. 271). 



279. General Structure of the 

 Skin. The skin is divided into 

 two distinct layers, which may 



be readily separated : the deeper layer, the true skin, 

 dermis, or corium ; and the superficial layer, or outer skin, 

 the epidermis, cuticle, or scarf skin. In some parts of the 

 body the skin is closely attached to the structures beneath, 

 while in others it is less firmly adherent and rests upon a 

 variable amount of fatty tissue. It thus assists in relieving 



FIG. 94. Diagrammatic Scheme 

 to illustrate in a very General 

 Way Absorption and Excre- 

 tion. 



A, represents the alimentary canal; 

 Z,, the pulmonary surface ; K, the 

 surface of the renal epithelium; 

 S, the skin ; a, oxygen ; A, hydro- 

 gen ; , nitrogen. 



