THE GLANDS OF THE SKIN. 



397 



Nucleus of 

 nonstriated 

 muscle-cell. 



of the coil. In figure 319 are shown two views of a model of the 

 coiled portion of a sweat-gland from the plantar region of the foot 

 of a man. The length of the tubule in the coiled portion of this 

 gland measures 4.25 mm., of which 1.25 mm. fall to the excretory 

 duct and 3.0 mm. to the secretory tubule. 



The blind end of the secreting portion of the tubule and the ex- 

 cretory duct as it enters the coil are usually in close proximity. 

 The secretory portion of the tubule of sweat-glands is lined by a 

 single layer of cubic or columnar cells, with finely granular proto- 

 plasm and round or oval nuclei possessing one or two nucleoli. Be- 

 tween this layer of cells and the basement membrane there is found 

 a layer of nonstriated muscle-cells, longitudinally disposed. The 

 portion of the excretory duct found within the coil of the glands 

 is lined by a single layer of short cubic cells, with cuticular border, 

 outside of which there is a delicate basement membrane. The 

 muscular layer is lacking in 

 this and the remaining portion 

 of the duct. The excretory 

 portion of the duct passing 

 through the corium is lined 

 by short, somewhat irregu- 

 larly cubic cells arranged in 

 two layers. 



Capillary networks sur- 

 round the secreting portions 

 of the sweat-glands. 



The nerves of the sweat- 

 glands have been studied with 

 the aid of the methylene-blue 

 method by Ostroumow, work- 

 ing under Arnstein's direction. 

 These glands receive their in- 

 nervation through the neur- 

 axes of sympathetic neurones, 



the terminal branches of which form an intricate network just out- 

 side of the basement membrane, known as the epilamellar plexus. 

 From this plexus fine varicose nerve-fibers pass through the base- 

 ment membrane, and, after coursing a shorter or longer distance 

 with or without further division, end on the gland-cells, often in 

 clusters of small terminal granules united by delicate threads. 



The development of the sweat-glands begins in the fifth month 

 of fetal life. At first solid cords grow from the stratum germi- 

 nativum of the epidermis into the corium. Later, in the seventh 

 month, these become hollow. 



Joseph has shown a structural change in the secretory cells 

 of the sweat-glands when perspiration was induced by electrical 

 stimulation or by drugs. 



With the sweat-glands as here described, and which have, as 



Fig. 321. Tangential section through 

 coiled portion of sweat-gland from human 

 axilla. Sublimate fixation ; X 7- 



