278 ELEMENTS OF HISTOLOGY. [Chap, xxxiv. 



these essential respects, that its epithelium is a single 

 layer of transparent columnar cells, and that there 

 is between this and the limiting membrana propria 

 a layer of non-striped muscle cells (Kolliker) arranged 

 parallel with the long axis of the tube. In some 

 places, as in the palm of the hand and foot, in the 

 scrotum, the nipple of the breast, the scalp, but 

 especially in the axilla, this distal portion of the coiled 

 tube is of very great length and breadth, and its 

 epithelial cells contain a variable amount of granules. 

 It appears to me that the cells resemble in this 

 respect those of the serous salivary glands and the 

 chief cells of the gastric glands (Langley), inasmuch 

 as they produce in their interior larger or smaller 

 granules which are used up during secretion, from the 

 peripheiy towards the lumen. 



376. The cenimmoiis glands of the meatus 

 auditorius externus are of the same structure as the 

 distal portion just described, except that the inner 

 part of the cell protoplasm of the epithelium contains 

 yellowish or brownish pigment, found also in their 

 secretion, i.e., in the wax of the ear. 



Around the anus there is an elliptical zone, in the 

 skin of which are found large coiled gland tubes the 

 circumanal glands of A. Gay which are identical in 

 structure with the distal portion of the sweat gland 

 tubes. 



377. The sweat glands develop as a solid cylin- 

 drical outgrowth of the stratum Malpighii of the 

 epidermis, which gradually elongates till it reaches 

 the superficial part of the subcutaneous tissue, where it 

 commences to coil. The lumen of the tube is of 

 later appearance. The membrana propria is derived 

 from the tissue of the cutis, but the epithelium and 

 muscular layer are both derived from the original 

 outgrowth of the epidermis. 



378. The hair-follicles (Fig. 147). The skin 



