206 



SPECIAL HISTOLOGY. 



fatty granules, and still more frequently a small quantity of 

 yellowish or brownish pigment -granules. 



The thick-coated sudoriparous glandular canals (fig. 79 B) 



A 



Fig. 79. 



B 



a 



L 



possess, besides the two layers just described, a middle layer of 

 smooth muscles running longitudinally, whose elements are 

 easily separable, as muscular fibre-cells of 0-015 — 0'04"' long, 

 0-002 — 0-005, or even 0-008'" broad, occasionally, with a few 

 pigment-granules, and each containing a roundish elongated 

 nucleus. Whenever the glandular tubes contain only fluid, 

 the epithelium is a single very distinct layer of polygonal cells 

 of 0-006 — 0-015'"; in the opposite case it can be seen only with 

 difficulty, or not at all. With respect to the occurrence of 

 these two forms of glandular canals, the thick muscular walls 

 are found, especially in the large glands of the axilla, whose 

 cells all possess muscular walls, and thence acquire a very 

 peculiar striated appearance. I have noticed a precisely similar 

 structure only in the large glands of the root of the penis and 

 of the nipple, although it is true that there is occasionally 

 a muscular development, but slighter and only partial, in the 

 glands of the palm, whose wide canals are distinguished by the 

 thickness of their walls, and exhibit a muscular structure dis- 



Fig. 79. Sweat ducts, x 350. A, one with thin walls and a central cavity, with- 

 out a muscular coat, from the hand : a, connective investment ; b, epithelium ; c, 

 cavity. B, a portion of a canal without a cavity, and with a delicate muscular layer, 

 from the scrotum : a, connective tissue ; 5, muscular layer ; c, cells, which fill the 

 glandular canal with yellow granules among their contents. 



