XXIX.] THE SKIN. 319 



shaped, devoid of prickles, and are crowded with granules of eleidin. 

 a substance, apparently one of the stages on the way to the hotly 

 keratin. These cells stain deeply with picro-carmine, haematoxylin, 

 and osmic acid. They are soluble in caustic potash, and in this 

 respect differ from keratin. 



(iii.) The stratum Iwidum is composed of two or more layers of 

 flattened transparent cells, with no prickles, and free from granules, 

 but with a horizontally-placed, rod-shaped nucleus. They do not 

 stain readily. 



(iv.) The stratum corneum or horny layer consists of horny 

 sijuames composed of keratin (Lesson IV.). 



(e.) The sweat-glands are most numerous in the palm of the 

 hand and sole of the foot. Each gland is a simple tube coiled up 

 at its lower extremity into a coil -^ inch in diameter. To see their 

 whole course coil and duct the sections must not he too thin, 

 and should be parallel to the course of the gland. The coil of the 

 gland lies in the subcutaneous tissue. The secretory part of the 

 tube consists of a basement membrane lined by a single layer of 

 nucleated transparent cubical or columnar cells surrounding a small 

 but distinct lumen. Between the epithelium and the basement 

 membrane is a longitudinally- 

 disposed layer of smooth 

 muscular fibres. The coil 

 also contains a part of the 

 sudoriferous canal or duct 

 (fig. 308). The latter is 

 narrower than the secretory 

 part, and consists of a base- 

 ment membrane lined by 

 several layers of polyhedral 

 cells. There is no muscular 

 layer, but internal to the 



.,, ,. if.'. FIG. ^08. Section of Part of Coil of a Sweat- 



opithelial lining there is a Glar ? d . . Duct; s. Secretory part, x 3 oo. 

 delicate membrane or cuticle. 



Trace the coil into its duct, which runs vertically through the cutis 

 vera with a slightly wavy course. It has a basement membrane 

 lined by two or three layers of short cubical cells, which, if traced 

 upwards, become continuous with those of the Malpighian layer of 

 the epidermis, looking like a funnel-shaped expansion. The lumen 

 of the duct is distinct. The bwrnent membrane becomes continuous 

 with the altered superficial layer of the corium just under the epi- 

 dermis. The lumen of the duct is continued upwards in a corkscrew 

 spiral through the epidermis. A complete view of its course is only 

 obtained in a thickish section. In a thin section the twistings are 

 of course divided. 



