DIGESTION 337 



thick and rich in organic matter. With strong stimulation 

 of both nerves, the secretion, at first plentiful and watery, 

 soon diminishes, even below the amount obtained by 

 stimulation of the chorda alone, perhaps because of the 

 diminution in the blood-flow produced by the vaso-con- 

 strictors of the sympathetic. With stimulation just strong 

 enough to cause secretion when applied separately to either 

 nerve, there is no secretion when it is applied simultaneously 

 to both. 



All this refers to the dog. In this animal, then, there 

 seems to be a certain amount of physiological antagonism 

 between the secretory action of the two nerves. But it 

 differs in one respect from the antagonism between their 

 vaso-motor fibres ; for with strong stimulation the con- 

 strictors of the sympathetic always swamp the dilators of 

 the chorda, while the secretory fibres of the chorda appear 

 upon the whole to prevail over those of the sympathetic. 

 And in all probability this apparent secretory antagonism is 

 very superficial ; and whatever interference there may be 

 between the two nerves, apart from any possible effect of 

 their vaso-motor interference, is not due to the one annulling 

 the influence of the other on the gland-cells, but to the cells 

 being called by them to different labours, in general com- 

 plementary to each other, and only incompatible in so far as 

 the working power of the cells may not be able to respond 

 at the same time to large demands from both sides. For 

 the sympathetic always adds something to the common 

 secretion when there is a secretion at all, this something 

 being represented by an increase in the percentage of 

 organic matter. Not only so, but the sympathetic effect 

 persists after stimulation has been stopped ; and excitation 

 of the chorda after previous stimulation of the sympathetic 

 causes a flow of saliva richer in organic matter than would 

 have been the case if the sympathetic had not been 

 stimulated. 



Indeed, the distinction between chorda and sympathetic 

 saliva, which, by taking account of the parotid as well as the 

 submaxillary and sublingual glands, has been generalized 

 into a distinction between cerebral and sympathetic saliva, 



22 



