3 5^ NORMAL HISTOLOGY AND ORGANOGRAPHY. 



trates to the lower stratum of the skin, or even deeper, 

 to the subcutaneous connective tissue. This distal 

 end is very much coiled and constitutes the secreting 

 portion of the gland. In the epidermis the duct has 

 no other wall than the epithelial cells of the various 

 layers through which it passes, but in the dermis the 

 wall is composed of a single layer of short cubical cells 

 outside of which there is a delicate basement mem- 

 brane. The secreting 

 portion is also lined by 

 simple epithelium, but 

 the cells are larger and 

 have a finely granular 

 protoplasm. Between the 

 gland cells and the base- 

 ment membrane there 



Fig. 250. Cross section of deep ... . , , 



portion of sweat gland. is found in the larger 



glands, a single layer of 



non-striated muscle cells arranged longitudinally. 

 This muscle is derived from the ectoderm, while the 

 other musculature of the body comes from the meso- 

 derm. The muscle of the sweat glands probably 

 aids these glands in expelling their products of secre- 

 tion. Non-medullated nerve fibers of the sympa- 

 thetic system form a delicate network just external 

 to the basement membrane called the epilamellar 

 plexus. From this plexus delicate fibers pass 

 through the basement membrane to ramify between 

 the gland cells, where they end in clusters of small 

 terminal granules. The physiological activities of 

 the sweat glands are thus directly under the control 

 of the nervous system and do not depend on the 



