NAILS. 417. 



the dermis to the side of the hair follicles. The latter are 

 obliquely implanted in the skin so that the hairs lie down 

 on the surface of the Body, and the muscles are so fixed that, 

 when they shorten, they erect the hair and cause it to 

 bristle, as may be seen in an angry cat, or sometimes in a 

 greatly terrified man. Opening into each hair follicle are 

 usually a couple of sebaceous glands (p. 418). 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 epidermis, 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 whiteness 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. Behind, 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, anew one is produced, 

 provided the matrix is left. 



The Glands of the Skin are of two kinds, the sudori- 

 parous or sweat glands, and the sebaceous or oil glands. 

 The former belong to the tubular, the latter to the race- 

 mose type. The sweat-glands, Fig. 120, lie in the subcu- 



