THE SKIN 113 



ducts from which open into the mouths of the hair-follicles. Both the 

 duct and the saccules are lined by epithelium, which becomes charged 

 with fatty matter. This sebaceous matter is discharged into the cavity 

 of the saccule, probably owing to the disintegration of the cells within 

 which it is formed. There may be two or more sebaceous glands 

 attached to each follicle. 



The sebaceous glands are developed as outgrowths from the outer 

 root-sheath. 



The sweat-glands are abundant over the whole skin, but they are 

 most numerous on the palm of the hand and on the sole of the foot. 

 They are composed of coiled tubes, which lie in the deeper part of the 

 integument and send their ducts up through the cutis to open on the 

 surface by corkscrew-like channels which pierce the epidermis (fig. 137). 



FIG. 137. DUCT OF A SWEAT-GLAND PASSING THROUGH THE EPIDERMIS. 

 (Magnified 200 diameters.) (Heitzmann.) 



BP, papillae with blood-vessels injected ; V, rete mucosurn between the papillae ; E, stratum 

 oorneuiu ; PL, stratum grauulosum ; D, duct, opening on the surface at P. 



The glandular or secreting tube is a convoluted tube composed of 

 a basement-membrane lined by a single layer of cubical or columnar 

 epithelium-cells, and with a layer of longitudinally disposed plain 

 muscular fibres between the epithelium and basement-membrane. 

 It is considerably larger than the efferent tube or duct, which begins 

 within the gland and usually makes several convolutions before leaving 

 this to traverse the cutis vera. The efferent tube has an epithelium 

 consisting of two or three layers of cells, within which is a well- 

 marked cuticular lining, but there is no muscular layer. The passage 

 through the epidermis has no proper wall, but is merely a channel 

 excavated between the epithelium-cells. 



The ceruminous glands of the ear are modified sweat-glands. 



