534 THE HUMAN BODY 



couple of sebaceous or oil-glands. Hairs are found all over the skin 

 except on the palms of the hands and the soles of the feet; the 

 back of the last phalanx of the fingers and toes, the upper eyelids, 

 and one or two other regions. 



Nails. Each nail is a part of the epidermi's, with its horny 

 stratum greatly developed. The back part of the nail fits behind 

 into a furrow of the dermis and is called its root. The visible part 

 consists of a body, fixed to the dermis beneath (which forms the 

 bed of the nail), and of a free edge. Near the root is a little area 

 whiter than the rest of the nail and called the lunula. The white- 

 ness is due in part to the nail being really more opaque there and 

 partly to the fact that its bed, which seen through the nail causes 

 its pink color, is in this region less vascular. 



The portion of the corium on which the nail is formed is called 

 its matrix. Posteriorly this forms a furrow lodging the root, and it 

 is by new cells added on there that the nail grows in length. The 

 part of the matrix lying beneath the body of the nail, and called 

 its bed, is highly vascular and raised up into papillae which, except 

 in the region of the lunula, are arranged in longitudinal rows, 

 slightly diverging as they run towards the tip of the finger or toe. 

 It is by new cells formed on its bed and added to its under surface 

 that the nail grows in thickness, as it is pushed forward by the new 

 growth in length at its root. The free end of a nail is therefore its 

 thickest part. If a nail is "cast" in consequence of an injury, or 

 torn off, a new one is produced, provided the matrix is left. 



The Glands of the Skin are of two kinds, the sudoriparous or 

 sweat-glands, and the sebaceous or oil-glands. The former belong 

 to the tubular, the latter to the racemose type. The sweat-glands, 

 Fig. 145, lie in the subcutaneous tissue, where they form little 

 globular masses composed of a coiled tube. From the coil a duct 

 (sometimes doubb) leads to the surface, being usually spirally 

 twisted as it passes through the epidermis. The secreting part 

 of the gland consists of a connective-tissue tube, continuous along 

 the duct with the dermis; within this is a basement membrane; 

 and the final secretory lining consists of several layers of gland- 

 cells. A close capillary network intertwines with the coils of the 

 gland. Sweat-glands are found on all regions of the skin, but 

 more closely set in some places, as the palms of the hands 

 and on the brow, than elsewhere: there are altogether about 



