310 MATHEWS. 



Cat. Cat. Dog. 

 I. II. 

 Amoicnt. Amount. 

 1st stimulation . .20 l6 36 



Rest .... 25 seconds i minute 2 minutes. . . . 



2d stimulation . . . . o 6 25 



Rest .... 3 minutes 2 minutes . . . . i minute .... 



3d stimulation .... il 10.5 H 



Rest 2 minutes . . . 



4th stimulation lo . . . . . 



Rest I minute .... 



5 th stimulation , 11 .... 



Rest . . . • I minute .... 



6th stimulation 2.5 .... 



Rest Chorda stimulated . 



7th stimulation 25 .... 



Rest 2 minutes . . . 



8th stimulation 6 .... 



Rest I min. 40 sec. . . 



9th stimulation 4 . . • . 



The great decrease in the amount of sahva obtainable on a 

 second stimulation, closely following a first, even though a min- 

 ute's intreval of rest elapse, might be explained on Heidenhain's 

 theory, by assuming an exhaustion of secretory fibres, nerve 

 ends or gland cells. Such an assumption is highly improbable. 

 There is, I believe, no other example of a nerve end, or fibre, 

 becoming exhausted by a weak stimulus of a minute's duration. 

 That the secretory fibres of the chorda, their nerve ends and 

 the gland cells are not exhausted or suffocated is shown by the 

 fact that the following chorda stimulation is little, if at all, al- 

 tered. The phenomena are clearly explicable, on the other 

 hand, if the sympathetic causes secretion by compression of the 

 ducts and alveoli. By the first stimulation the gland is largely 

 emptied of its saliva. If no time be given for the ducts to be 

 refilled, the following stimulation finds less available saliva, or 

 none at all. The nerve appears, in fact, to have become inoper- 

 ative until, through the resting of the gland, or the action of the 

 chorda, the ducts be again filled. The exhausted element of 

 the gland inferred by Heidenhain is the fluid in the ducts and 

 alveoli. 



