GLANDS, GENERAL PHYSIOLOGY OF SECRETION. 259 



easily demonstrated in the case of the pancreas and the mu- 

 cous glands only, and that its application to other glands is 

 upon probable grounds only. 



THE INNERVATION OF GLANDS. 



That glands are under direct nervous control is a matter 

 of every-day experience. The tear glands respond at once 

 to intense emotions, and the common expression to have 

 one's "mouth water" shows that the salivary glands are di- 

 rectly influenced by states of mind. Such nervous influ- 

 ences are not so apparent in the case of the sweat glands, 

 but even there intense emotion or anxiety may produce a 

 copious sweating even when the surrounding temperature 

 would tend the other way. In the case of the stomach 

 and pancreas there are such evidences of innervation. Se- 

 cretion in the stomach at once induces secretion in the pan- 

 creas, explained only by the fact that these two organs are 

 connected by nerves. There is no more reason why glands 

 should be automatic, that is, independent of nervous con- 

 trol, than why muscles should be. Glandular activity is no 

 less an activity than muscular exertion. The regulation of 

 the periods of secretion so that the product may be availa- 

 ble just at the moment that it is needed could be effected 

 only by nervous control. The saliva flows when food is 

 masticated in the mouth, the gastric or pancreatic juices 

 are poured into the alimentary canal as soon as the mucous 

 membrane in stomach and intestine is stimulated by enter- 

 ing foods, while the gall-bladder contracts and pours its 

 contents of bile into the duodenum for the same reason. 



The manner of the innervation of glands has, however, 

 been worked out carefully and explicitly in the case of the 

 salivary glands only, and the account here given is that of 

 the submaxillary gland itself, but there is every reason to 

 believe that in the main the nervous arrangement of the 

 other glands is the same. In order to understand how this 

 has been worked out, a few experiments in the stimulation 



