ANATOMY OF THE SKIN. Ill 



As the skin presents such a variety of functions, its 

 physiological anatomy is most conveniently considered in 

 connection with different divisions of the subject of physi- 

 ology. For example, under the head of secretion, we have 

 already taken up the structure of the different varieties of 

 sebaceous glands. The anatomy of the skin as an organ of 

 touch will be most appropriately considered in connection 

 with the nervous system. In this connection we will describe 

 the excreting organs found in the skin ; and here it will be 

 most convenient to study briefly its general structure and the 

 most important points in the anatomy of the epidermic ap- 

 pendages. A full and connected description of the skin and 

 its appendages belongs properly to works upon anatomy. 



General Appearance of the Skin. It is unnecessary to 

 discuss very minutely the general appearance of the skin. 

 Its color is sufficiently familiar. The tissue of the true skin 

 is whitish and semitransparent, so that the color of the sub- 

 jacent parts gives to it a peculiar tint. The blood contained 

 in its vessels, as is well known, is capable of modifying 

 greatly the color of the general surface. The deep layer of 

 the epidermis always contains more or less pigmentary mat- 

 ter, which gives the colors characteristic of different races, 

 and produces the variations in complexion that are observed 

 in different individuals of the same race. The pigment, in 

 the white races, is but slightly developed at birth, but in- 

 creases in quantity with age. 



The general surface, with the exception of the palms of 

 the hands and the soles of the feet, is covered with hairs, 

 which are very largely developed in certain situations. The 

 furrows and folds of the skin are produced either by the con- 

 traction of the subjacent muscles ; by a loss of elasticity in 

 the skin, as in old age ; by an excessive development of fat 

 in certain parts ; or by the movements of the joints. Faint, 

 irregular lines are observed on the surface in most parts j but 

 upon the palms of the hands and the soles of the feet these 



