446 



THE HUMAN BODY. 



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 sudo- 

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

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

 mose type. The siv eat- glands, Fig. 138, lie in the subcu- 

 taneous tissue, where they form little globular masses com- 

 posed of a coiled tube. From the coil a duct (sometimes 

 double) leads to the surface, being usually 

 spirally twisted as it passes through the epi- 

 dermis. The secreting part of the gland 

 consists of a connective-tissue tube, continu- 

 ous 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 inter- 

 twines 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 two 

 and a half millions of them opening on the 

 surface of the Body. 



The sebaceous glands nearly alwavs open 



.,,.,,., , -i I gland. d, horny 



into hair-follicles, and are lound wherever layer of cuticle; c, 



there are hairs. Each consists of a duct 



opening near the mouth of a hair-follicle 



and branching at its other end : the final 



branches lead into globular secreting saccules, mis - 



which, like the ducts, are lined with epithelium. In the 



FIG. 138. A sweat 



iiB 



