358 MATHEWS. 



f. CoNXLusiox. The Physiology of Salivary Secretion. 



If the sympathetic saHvary secretion shall be found to be due 

 to the action of contractile tissue, and if the criticisms of the ob- 

 jections to considering the salivary secretion, coincident with 

 vascular dilation, an osmosis, be sustained by subsequent work, 

 the following conclusions concerning the physiology of this 

 secretion may be drawn. 



The saliv^ary glands may be caused to secrete, either by the 

 action of contractile tissue under control of the sympathetic 

 nerve or by osmosis under control of the vaso-dilator nerve. 

 Probably in normal secretion both of these nerves come into 

 play, but of this evidence is as yet lacking. 



Drugs, or other reagents, may arouse secretion by action on 

 either or both of these mechanisms. I would suggest that 

 secretion following strychnine injection, camphor, pikrotoxin, 

 physostigmin (after division of the chorda) are due to the con- 

 tractions of the contractile tissue. All of these drugs stimulate 

 the nerve centers and cause a pronounced vaso-constriction. 

 On the other hand, pilocarpine, nicotine, muscarine, curare and 

 chloral hydrate, or other drugs with a similar action on the 

 vascular system, probably cause secretion partly by vaso-dila- 

 tion and partly by increasing the permeability of the gland mem- 

 branes. Such drugs work through an osmotic mechanism. A 

 third class of drugs, such as quinine, atropine, hydrochloric acid 

 or sodium carbonate may produce vaso-dilation, but probably act, 

 also, on the gland cells in such manner as to diminish their per- 

 meability- Most of the work which has hitherto been done 

 upon the action of drugs on salivary secretion needs to be re- 

 peated with the possibility in mind that the chorda and sym- 

 pathetic induce secretion in these different ways. 



The osmotic mechanism of secretion in the salivary glands is 

 probably dependent on the condition of the gland and capillary 

 membranes, upon the composition of the blood, upon the rate 

 of flow of the blood and the character and amount of hylogens 

 present within the gland. The evidence that the course of os- 

 mosis is controlled by the action of nerves directly on the gland 



