Organs of the Senses. 



THE Organs of the Senses are the instruments by which the mind is brought 

 into relation with external objects. These organs are five in number, viz., the 

 organs of touch, of smell, of taste, of hearing, and of sight. 



THE SKIN. 



The skin is the principal seat of the sense of touch, and may be regarded as a 

 covering for the protection of the deeper tissues ; it is also an important excretory 

 and absorbing organ. It consists of two layers, the derma or cutis vera, and the 

 epidermis or cuticle. On the surface of the former layer are the sensitive 



Fig. 297. A Sectional View of the Skin (magnified). 



papillae j and within, or imbedded beneath it, are the sweat-glands, hair-follicles, 

 and sebaceous glands. 



The derma or true skin is tough, flexible, and highly elastic, being admirably 



adapted to defend the internal parts from violence. It consists of fibro-areolar 



tissue, intermixed with numerous bloodvessels, lymphatics, and nerves. The 



fibro-areolar tissue forms the framework of the cutis ; it is composed of firm 



602 



