FUNCTIONS OF THE SWEAT-GLANDS. 277 



capillaries), will appear. This process implicates, however, the 

 participation of a certain though limited degree of mechan- 

 ical force, along with the enhanced metabolism brought about 

 by the quantity of oxidizing plasma present in the active local 

 process induced. 



A brief summary of the histology of this system is neces- 

 sary, however, to illustrate the various features to be studied. 

 The capillaries form a close net-work around the coiled tubes, 

 and reach down to an extremely thin basement membrane, 

 which, in turn, surrounds the layer of muscular fibers that coil 

 around these tubes. An important feature of this muscular 

 layer, which is only separated from the cavity or lumen of 

 the tube by the secreting epithelial cells and their endothelial 

 lining, however, is that its ribbon-like fibers are spirally 

 wrapped round the tube, and in such a manner as to leave a 

 gap between their border, throughout their whole length. Not 

 only, therefore, is the thin basement membrane thus enabled 

 to reach the secreting cells through the gaps, but the former 

 actually project through the latter so as to touch the mem- 

 brane. Furthermore, the projecting cells are so related to one 

 another as to form canaliculi-like spaces, which extend from 

 the capillary-covered membrane completely through to the 

 lumen of the tube (Eanvier). The mechanism of the sweat- 

 secretion is not difficult to understand if these facts are borne 

 in mind: Contraction of the muscle not only shortens the tube 

 longitudinally, but causes it to contract when the oxidizing 

 plasma in the capillaries is increased through peripheral vas- 

 cular engorgement, whether this be due to constriction of the 

 arterioles from which the capillaries arise or to contraction of 

 the central vascular trunks. Both sources of peripheral blood- 

 pressure act in precisely the same manner: They engorge the 

 tubular capillaries, excite the functional metabolism of the 

 underlying muscles, and force the glandular secretion into the 

 tubular lumen and up along the duct to the cutaneous sur- 

 face. We can readily understand, therefore, why pilocarpine 

 should, by stimulating the anterior pituitary and through it 

 the adrenals, give rise to profuse sweating. 



The experiments of Luchsinger, undertaken with other 

 phases of the problem in view, may also be used in this con- 



