372 HUMAN ANATOMY. 



5. Superior laryngeal, filaments from its internal branch to 

 the base. 



THE SKIN AND APPENDAGES. 



The skin, besides being the special organ of the sense of 

 touch, is an absorbing and excretory organ, and protects the 

 underlying structures. 



It consists of two layers the epidermis or cuticle, and 

 the derma or true skin. The appendages are the nails, hair, 

 sudoriferous and sebaceous glands, and their ducts. 



The epidermis,, or cuticle, is an epithelial structure consist- 

 ing of four layers : 



1. Rcte Malpif/Jiii, the deepest layer, in contact with the cerium, is 

 composed of several layers of round or polyhedral epithelial cells. This 

 layer is pigmented in the negro and other dark races. 



2. Granular layer, is a single layer of compressed, spindle-shaped 

 cells. 



3. Stratum lucidum, are still more compressed into scales. 



4. Stratum corneum, several layers of horny scales. 



The derma, or true skin, has two layers, the reticular or 

 deeper, and the papillary or superficial. 



Reticular layer is composed of interlacing bands ef white 

 fibrous tissue, mixed with yellow ..elastic fibres, and some un- 

 striated muscular fibres where hairs are found, together with 

 blood-vessels, lymphatics, and nerves, 



Papillary layer is covered with minute, vascular, highly sen- 

 sitive elevations the papillse from one one-hundredth to one 

 two-hundred-and-fiftieth of an inch in diameter. These papillae 

 are in places arranged into parallel curved ridges, and have in 

 the most sensitive situations some one of the "peripheral end 

 organs" (already described) added to their structure. 



NAILS are horny plaques of modified epidermis, firmly 

 adapted to the derma on the dorsal surfaces of the terminal 

 phalanges. Each nail is firmly implanted by its root into a fold 

 of skin. 



The matrix is the derma beneath the body, which is vascular 

 and highly sensitive. 



The lunula is the white, less vascular portion of the matrix 

 near the root. 



HAIRS are a cylindrical modification of the epidermis, and 

 consist of a root imbedded in the skin, a shaft, and a point. 



Root is lodged in a pouch-like involution of epidermis the 

 hair-follicle. This is composed of an inner or cuticular and an 



