OF THE GLANDS OF THE SKIN. 205 



where it dilates to about double the size, i. e., to 0-024-0-28 of a line 

 (Fig. 80); retaining this breadth, it traverses the epidermis, and ter- 

 minates in an aperture of 513^ of a line. In the axillary glands, the 

 excretory duct measured in one case at the level of the sebaceous 

 glands 0'06-0*09 of a line, immediately under the epidermis 0*03, in the 

 epidermis itself 0'06 of a line. In the corium the sweat-ducts have 

 always a distinct cavity, an external investment of connective tissue, 

 with elongated nuclei (in the glands of the axilla, muscles also), 

 at all events, inferiorly, 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 dis- 

 posed 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, 

 corresponding w T ith 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 w r ith 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 of embryonic life, and are originally 

 perfectly solid, slightly flask-shaped, processes 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 0*09 of a line in length, and 0-01 

 of a line in breadth at the neck, at the bottom 0-018-0-02 of a line, 

 and even the very longest did not penetrate more than half through the 

 cutis, which was 0-25 of a line thick. They were entirely composed of 

 round cells, perfectly similar to those of the stratum Malpighii of the 

 epidermis ; besides which, each process had a delicate investment, which 

 was continuous with the boundary of the inner surface of the epidermis. 

 No trace of sweat-pores or ducts was visible. At the beginning of the 

 sixth month, the glands in the sole of the foot and palm of the hand 

 extend as far as the middle and inner fourth of the cutis, measure at 

 the clavate extremity 0-028-0-04 of a line, and 0-016-0-02 of a line in 

 the duct which arises from them, are already slightly serpentine, and 

 present a cavity, at all events partially in their narrow portion; they 

 do not, however, penetrate the cuticle, or in any way open on the 



