SECRETION PHYSIOLOGY. 359 



cells is open to serious criticism. That chorda saliv^ary secre- 

 tion can ensue without vaso-dilation may be seriously doubted, 

 not only for the reasons already stated, but because in the 

 pancreas there is good reason to believe that secretion can not 

 take place without vaso-dilation. (See p. 361.) 



V. SOME OTHER SECRETIONS. 



The submaxillary gland, considered in the foregoing pages, 

 may be taken as a type of all the salivary glands, as each pos- 

 sesses a dilator secretory nerve, and a constrictor, sympathetic 

 secretory nerv^e. I wish now to consider some other secretion in 

 the light of the conclusions derived from the physiology of the 

 submaxillary. 



a. The Physiology of Sweat Secretion. 



There is reason to believe that the mammalian sweat glands 

 also have a double mechanism of secretion, a muscular and an 

 osmotic. These glands are surrounded by a sheath of muscle 

 fibres lying, like those of the skin glands of amphibia, be- 

 tween the cells and the basement membrane. From the obser- 

 vations of Ranvier, Joseph and others, who have shown that 

 upon stimulation of the sciatic this muscle contracts, there can 

 be little doubt that a secretion may thus be formed. Probably 

 sweat secretions ensuing coincident with vaso-constriction, upon 

 the injection of strychnine, upon stimulation of the sciatic in the 

 amputated limb or after compression of the blood vessels is due 

 to this mechanism. 



On the other hand, certain secretions of sweat are too copi- 

 ous to be due to muscular constriction of the gland. That 

 those secretions probably fall under the second, or osmotic, 

 mechanism is shown by the following facts : 



(i) The coincidence of vaso-dilation and sweat secretion. 

 Most sweat secretions are normally accompanied by vaso-dila- 

 tion. If the cervical sympathetic of the horse be severed, 

 strong' hypersemia and sweating occurs on the side of the neck 

 the nerve governs. This sweating ensuing after nerve division 



