NERVOUS SYSTEM UPON SECRETION 277 



stomach is capable of preparing its specific secretion in the absence 

 of vagal influence. 



But, as Pawlow points out, this does not settle the problem as 

 to whether the vagus contains fibres which influence the secretion, 

 and he adduces evidence going to show that the vagus probably 

 contains both excitatory and inhibitory fibres for the secreting 

 cells of the stomach. 



It is only by careful comparison of the secretory activity of 

 the stomach before and after vagotomy, and by stimulation of 

 the peripheral end of the nerve in such a manner, or after such 

 procedures, that other effects upon the heart, etc., are not excited, 

 that we can judge as to any possible effect upon secretion. 



Previous to Pawlow's more detailed experiments as to the 

 paths along which efferent stimuli pass to the secreting cells, it 

 had been shown fairly clearly that the gastric secretion could be 

 called forth by reflex nervous mechanism. Thus Richet showed 

 in the case of a boy with an inoperable and complete stricture 

 of the oesophagus occasioned by swallowing caustic alkali, upon 

 whom a gastrotomy had been performed, that soon after taking 

 anything sweet or acid into the mouth a secretion of pure gastric 

 juice occurred, which could accordingly only be excited by a reflex 

 nervous stimulus. Bidder and Schmidt also showed that the 

 sight of food to a dog with a gastric fistula led to a flow of gastric 

 juice. The experiment of Richet was, however, an isolated one, 

 and in those of Bidder and Schmidt the stimulus might have 

 been a direct one due to swallowed saliva. 



To Pawlow belongs the credit of having devised most ingenious 

 methods for studying the secretion of the gastric juice; the reflex 

 influence of the nervous system upon the secretion, and the efferent 

 path by which the reflex travelled ; as also the effects of different 

 forms of food upon the amount and properties of the secretion. 



A method for studying the secretion apart from any influence 

 of the contact of saliva or swallowed food was obtained by making 

 a fistula of the oasophagus in the neck- in addition to the usual 

 gastric fistula. After the double operation the effect of " physical " 

 stimulation could be studied by showing appetising food to the 

 animal but not allowing it to chew or swallow it, when a copious 

 flow of gastric juice resulted after a latent period of about five 

 minutes. Also the effect of sham feeding was investigated, in which 

 the animal, in addition to being shown the food, was allowed to 



