436 PRACTICAL ANATOMY. 



The Schneiderean mucous membrane is closely ad- 

 herent to the periosteum. It is continuous with the skin 

 of the face at the anterior nares, and continuous with 

 the mucous membrane of the pharynx at the posterior 

 nares. It is also continuous with the mucous lining of 

 the lachrymal duct, the frontal, sphenoidal, and maxillary 

 sinuses. It is thick and vascular over the turbinated 

 bones and septum nasi. Anteriorly the epithelium is 

 squamous. In the inferior meatus it is ciliated ; above 

 it is columnar and imbedded in it are the olfactory cells, 

 which consist of spindle-shaped, nucleated cells having 

 an external hair-like process which projects slightly 

 above the level of the mucous membrane. The other 

 extremity is continuous with a filament of the olfactory 

 nerve. Numerous mucous crypts are imbedded in the 

 mucous membrane, and in the walls are seen spheroidal 

 nucleated cells which appear to be intimately associated 

 with the branches of the olfactory nerves. 



THE SKIN. 



The skin is the fibre-elastic investing structure of the 

 body. It is the organ of touch and contains the sweat 

 and sebaceous glands and hair-follicles, and serves for 

 the protection of the deeper structures. It is thickest 

 on the sole of the foot and palm of the hand and on the 

 back, and thicker on the outer than the inner surface of 

 the extremities. It is thinnest on the eyelids and penis. 

 Its average thickness is about -^ inch. It is divided 

 into two layers, the superficial and deep. The former 

 is called the epiderm, the latter the cutis vera. Each of 

 these is subdivided into two layers ; the epiderm into a 

 superficial called the stratum corneum, and a deep layer, 

 the rete mucosum. The layers of the cutis vera are the 



