134 W- M - Bayliss and J. E. Bradford, 



In the cat we have only made one experiment and in this, as in 

 the dog, on stimulation of the tympanic plexus, a deflection showing 

 the duct to become positive to the surface was obtained. On stimu- 

 lation of the sympathetic, a diphasic variation was observed and in 

 both cases a fair amount of saliva was secreted x ). 



General remarks. 



With regard to the cause of the differences of potential which we 

 have above described the most obvious explanation is, that some of 

 the effects are due to the contraction and relaxation of the muscular 

 coat of the arteries of the gland, owing to the chorda and sympathetic 

 containing vasomotor fibres. It is however easily seen that this view 

 is untenable, since the chorda-effect in the dog is completely abolished 

 by' very small doses of atropine, by which the vasomotor effects of 

 nerve-stimulation are quite unaffected. It may further be urged that 

 although the chorda -effect in the dog is due to secretory processes 

 the sympathetic effect in the same animal is due to vasomotor changes. 

 There are indeed facts that appear to lend some support to this view, 

 such as the long latent period and small amplitude of the sympathetic- 

 effect in the dog, and the fact that it is very refractory to atropine, 

 but on the other hand there are many others opposed to it. For it 

 must be remembered that the secretory effects of sympathetic -stimu- 

 lation are also very refractory towards atropine, although these 

 effects may at length be abolished. The electrical effects may fairly 

 be expected to persist for a short time after all obvious secretion has 

 ceased, since the production of an electrical variation is probably a 

 more delicate test of the continued activity of the nerve-fibres, than 

 the existence of an obvious secretion. 



But the most important fact against this view is that in the cat 

 the sympathetic effect is not only comparatively easily abolished by 

 atropine, but that instead of being opposite in character to the chorda 

 effect, it resembles it greatly, although presenting certain differences 

 that have been mentioned above. Thus in the cat, where as is known 

 the secretory effect of the sympathetic is very different from that in 



') In the parotid of the cat, as well as in the submaxillary, excitation of the 

 sympathetic causes a copious watery secretion. 



