194 VISCERAL ANATOMY. 



Papillary Layer ; situated next to the rete mucosum, is covered with minute 

 conical elevations (papillae), T 7 inch high ^ inch in diameter at their 

 base, very numerous and arranged in parallel curved lines wherever sen- 

 sibility is greatest. Each papilla contains a capillary loop or plexus, the 

 termination of one or more sensory nerves, and in highly sensitive parts, 

 an oval shaped body, the Tactile Corpuscle. 



Corium, the lower layer of the derma, is composed chiefly of interlacing 

 bundles of white fibrous tissue, in which are mingled some yellow elastic 

 fibres, also plain muscular fibres wherever hairs are found, and lym- 

 phatic vessels, blood-vessels and nerves, in plexiform arrangement. 



Describe the Nails. They are flat, horny structures, a modification of 

 the epidermis, molded upon the derma at the dorsal surface of the terminal 

 phalanges of both fingers and toes. Each nail is convex on its outward 

 surface, and is imbedded by its Root into a fold of the skin. Its 



Matrix, is that portion of the derma directly beneath the nail. It is 

 covered with highly vascular papillae. The 



Lunula,\s a white crescentic portion of the nail nearest to its root, pro- 

 duced by the diminution in number and size of the papillae beneath. 



What are the Hairs ? They are also a modified form of the epidermis, 

 found over nearly the whole surface of the body, much varied in size and 

 color. Each hair consists of a Root and a Shaft. The 



Root, is lodged in an involution of the epidermis called the Hair -follicle, 

 which sometimes extends into the subcutaneous cellular tissue. The root 

 rests on a vascular papilla at the bottom or Bulb of the follicle, which 

 supplies it with the material for its growth. 



Shaft, is the projecting portion of the hair. It consists of a medulla in 

 the centre, next a fibrous portion, externally a cortex of thin, fiat scales. 

 The finest hairs have no medulla. 

 Point, consists of the fibrous portion and the cortex, the medulla being 



wanting. 



Where are the Sebaceous Glands most abundant ? In the scalp, the 

 face, around the anus, and the apertures of the nose, mouth and external ear. 

 The largest are the 



Meibomian Glands, situated in the eyelids (see Fig. 104). 



Describe the Sebaceous Glands. They are small, glandular bodies 

 situated in the corium or in the subcutaneous cellular tissue over most of the 

 body, but not in that of the palmar surface of the hands nor on the plantar 

 surface of the feet. Each gland consists of a single sacculated duct, usually 

 opening into a hair follicle, but sometimes ending on the surface of the in- 

 tegument. 



