OF THE GLANDS OF THE SKIN. 211 



006'". In the corium the sweat-ducts have always a distinct 

 cavity, an external investment of connective tissue, with elon- 

 gated nuclei (in the glands of the axilla, muscles also), at all events 

 iuferiorly, and an epithelium composed of at least two layers of 

 polygonal, nucleated cells without pigment granules. Where 

 the ducts enter the epidermis, they lose their investment of 

 connective tissue, which coalesces with the outermost layer of the 

 corium, and henceforward they are bounded by nothing but 

 layers of cells, which in the stratum Malpighii are nucleated, 

 but in the horny-layer are without nuclei. Chemically and 

 morphologically they completely resemble the epidermic cells,with 

 the sole exception that they are disposed more perpendicularly, 

 particularly in the horny-layer. The duct has often a distinct 

 cavity in the epidermis, at other times there is a granular streak 

 in the place of it, which is probably either a secretion or a deposit 

 from the secretion. The sweat-pores, whose disposition, cor- 

 responding with that of the glands, is sometimes very regular, 

 at others more irregular, are distinguishable, even with the 

 naked eye, in the palm of the hand and sole of the foot. In 

 other localities they are visible only with the aid of the 

 microscope; occasionally the excretory ducts of two glands unite 

 into a single canal (Krause). 



§ 70. 



Development of the sudoriparous Glands. — The sudoriparous 

 glands first appear in the fifth month Fig. 81. 



of embryonic life, and are originally «- 

 perfectly solid, slightly flask-shaped, pro- h 

 cesses of the stratum Malpighii of the 

 epidermis, and are very similar to the 

 first rudiments of the hair-sacs. In the 

 earliest condition which I have observed, 

 the processes measured in the sole of 

 the foot 0-03— 009"' in length, and 

 OOP" in breadth at the neck, at the 

 bottom 0-018 — 0-02'", and even the 

 very longest did not penetrate more 



Fig. 81. Rudiment of a sudoriparous gland of a human embryo at five months, 

 x 350: a, horny layer of the epidermis; b, mucous layer; e, corium; d, rudimentary 

 gland as yet without any cavity and consisting of small round cells. 



