NAILS HAIRS GLANDS. 467 



this surface, which correspond with the passage of hairs through 

 the cuticle, and with the openings of the perspiratory ducts. 



The Openings in the cuticle are the pores or openings for the per- 

 spiratory ducts, the openings for the passage of the hairs, and those 

 of. the sebaceous follicles. 



APPENDAGES TO THE SKIN. 



The appendages to the skin are the nails, hairs, sebaceous glands, 

 and perspiratory glands and ducts. 



The Nails are parts of the cuticle secreted in the same manner, 

 composed of the same material, but disposed in a peculiar way to 

 serve an especial purpose the protection, of the tactile extremities 

 of the fingers. They are inserted by their root into a deep groove 

 (matrix) of the skin, and are firmly attached to the papillary surface 

 by the close connexion of the, papillae with the longitudinal laminae. 

 The white semilunar segment near the root of the nail is called the 

 lunula. The cuticle is closely connected with it all round, and in 

 maceration the nail comes off with that layer. 



The Hairs have a very different structure and arrangement from 

 that of the nails : they are inserted for a considerable depth within 

 the integument, and terminate in conical or somewhat bulbous roots. 

 Each hair is enclosed beneath the surface by a vascular secretory 

 follicle, which regulates its form during growth. 



Hairs are very rarely completely cylindrical ; they are generally 

 more or less compressed, and somewhat prismoid in form. The 

 transverse section is reniform ; in texture it is dense and homoge- 

 neous towards the circumference, and porous and cellular in the 

 centre like the pith of a plant. 



The Sebaceous glands are abundant in some parts of the skin, as 

 in the armpits, the nose, &c., and vary in complexity of structure 

 from a simple pouch-like follicle to a lobulated gland. At the ex- 

 tremity of the nose they have several lobes } and in the scalp they 

 are lobulated like a bunch of grapes, and terminate in the follicles 

 of the hairs near to the surface of the skin. They secrete an oily 

 fluid which is poured out upon the surface of the skin, and tends to 

 preserve the flexibility of the cuticle. 



The Perspiratory ducts are minute spiral tubes which commence 

 in small lobulated glands, situated deeply in the integument beneath 

 the corium and among the adipose vesicles. They are easily seen 

 by examining a thin perpendicular section of the skin from the palm 

 of the hand, with a lens of moderate power. Proceeding from the 

 glands, the ducts ascend through the transverse furrow, between 

 the quadrilateral masses of papillce and through the rete mucosum 

 to terminate by open pores upon the surface of the cuticle. That 

 portion of the tube which is situated in the cuticle, is pretty equally 

 spiral ; but that below the level of the papillary surface is very irre- 

 gularly twisted, and is often nearly straight. In the scalp the tubes 

 are serpentine, or but slightly curved. 



