210 



SPECIAL HTSTOLOGY. 



Fig. 80. 



spiration ; nor have its pathological relations been investigated, 

 at all events not microscopically. 



§ 69. 



Sweat-Ducts. — The excretory ducts of the sudoriparous 

 glands, the sweat-ducts, or spiral-canals (figs. 45, 80), 



commence at the upper end 

 of the glandular coil as simple 

 canals, ascend with slight un- 

 dulations vertically through 

 the corium, and then penetrate 

 between the papilla (never 

 through their points), into the 

 epidermis. Here they begin 

 to twist, and according to the 

 thickness of the cuticle they 

 perform from 2 — 16 closer, or 

 more distant spiral turns, until 

 eventually they terminate by 

 small, round, often funnel- 

 shaped apertures, the so-called 

 sweat-pores on the free surface 

 of the epidermis. 



The length of the sweat- 

 ducts depends on the situa- 

 tion of the glands and the 

 thickness of the skin. The commencement of the duct 

 is invariably narrower than the canal in the coil itself, 

 measuring 0'009 — 0*012"'; it continues narrow up to its entrance 

 into the stratum Malpighii, where it dilates to about double the 

 size, i. e.j to 0'024 — 0-028"' (fig. 80) ; retaining this breadth, 

 it traverses the epidermis, and terminates in an aperture of 

 ± — JL'". In the axillary glands, the excretory duct measured 

 in one case at the level of the sebaceous glands 0*06 — 0"09'", 

 immediately under the epidermis 0'03'", in the epidermis itself 



Fig. 80. Perpendicular section through the epidermis and outer surface of the 

 corium of the bulb of the thumb, transversely through two ridges, x 50, and treated 

 with acetic acid : a, horny layer of the epidermis ; b, mucous layer ; c, cutis ; d, sim- 

 ple papilla; e, compound papilla; /, epithelium of a sweat-duct passing into the 

 mucous layer ; g, cavity of it in the cutis ; h, in the horny layer ; i, sweat-pore. 



