THE SKIN. 107 



The stratum granulosum contains cells more flattened than those of 

 the succeeding layer, and possesses granular particles, called eleidin, 

 which have an affinity for carmine. In the stratum, Malpighii, the 

 cells are rounded, or even columnar, in shape. Some of the cells 

 are connected by protoplasmic processes, which give rise to the so- 

 called prickle cells. In this layer occur the pigment granules that 

 give color to the skin. Beneath the epidermis is a basement mem- 

 brane. The corium comprises all that part of the skin underlying 

 the epidermis. It consists of two layers the stratum papillare and 

 the stratum reticulare. The stratum papillare contains the papillae, 

 which are conical elevations of the corium into the epidermis. They 

 are supplied with blood-vessels and nerves, a nerve-ending occurring 

 at the summit of each papilla. The corium is composed of fibrous 

 connective tissue, elastic fibres, blood-vessels, nerves, glands, and a 

 small amount of muscular tissue. The sebaceous glands are lo- 

 cated in the corium papillare, while the sudoriferous glands occur 

 in the corium reticulare or subcutaneous tissue. The corium rests 

 upon a subcutaneous structure, which consists chiefly of areolar, 

 adipose, and fibrous connective tissues. 



APPENDAGES. 



The nails. Nails are derived from the epidermis, and are com- 

 posed of horny cells. The structure of the nail comprises the body, 

 root, nail-bed, and matrix. The body, or exposed part, terminates 

 in a free-edge, while its sides are protected by the nail- walls. The 

 groove which receives the root is the nail-fold. That portion of the 

 epidermis upon which the nail rests is the nail-bed, and the basal 

 portion of the nail-bed upon which the root rests is the matrix. The 

 matrix and nail-bed are constituted of the stratum Malpighii, while 

 the body and root represent the stratum lucidum, the stratum cor- 

 neum being absent. The portion which is actively engaged in pro- 

 ducing the nail-body is the matrix. The nail, therefore, grows in 

 length, thickness, and width by the formation of new cells by the 

 matrix. The body consists of horny plates. 



The hair. Hair is a modification of the epidermis, and is pro- 

 duced by an infolding of the epidermis and a differentiation of the 

 lower cells of the follicle thus produced. The hair consists of two 



