Ill V«,l U \\l> MM'I.TITI 177 



tro] of the hunger mechanism, il is difficull to piece these together in 

 such a way as to formulate a simple theory which fits in with all the 



observed facts. We know that the stomach p in itself a local 



nervous mechanism by which, like the hearl or intestine, ii can auto- 

 matically perform many of the movements which arc exhibited in the 

 intact animal. These local movements may, however, he considerably 

 influenced by impulses transmitted to the stomach along the vagus and 



splanchnic nerves. We have therefore to seek for evidence indicating 



the relative importance of the local nervous mechanism in the stomach 

 itself and of the impulses transmitted to this organ by the extrL 

 nerves. We musl then seek the position of the center which p< 

 the sensation of hunger. 



It will he simplest to consider first the effect of section of the extrii 

 nerves in observations made on lower animals. Section <>i th< splancl 

 nerves increases gastric tonus and augments the gastric hunger contrac- 

 tions. Section of both vagus nerves, performed of course below the L< 

 of the heart, leaves the stomach in a more or less hypotonic condition. 

 The tonus is not entirely abolished; it varies somewhal from day 1" day. 

 and may become quite pronounced even though the vagi are cut. In 

 this hypotonic state the hunger contractions are diminished in 

 and regularity. Section of both the splanchnic and vagus nerves throws 

 the stomach into a permanent hypotonus, except in prolonged starva- 

 tion, when hunger contractions develop that are usually of great ampli- 

 tude and with particularly long intervals between the contractii 

 The genera] conclusion to hi' drawn from these experiments is that, 

 although completely isolated from the central nervous m, the 



stomach still exhibits typical hunger contractions, which must there! 

 1m- essentially dependent upon an automatic mechanism in the stomach 

 wall itself. Over this mechanism, extrinsic nerve impulses have merely a 

 regulatory conl rol. 



Variations and Inhibitions of the Hunger Contractions 



The afferent stimuli that may set up impulses traveling by the extrin- 

 sic nerves to the stomach are conveyed by the nei 

 psychic origin. Stimulation of the gustatory end organs in the mouth, 

 as by chewing palatable food, always causes an inhibition of the tonus 

 ami a diminution or disappearance of tin 1 hunger contractioi - the 



chewing of indifferent substances, Buch as paraffin, 



distinct inhibition, unless in a case in winch tl 



into a tetanus. It is of interesl that swallowing movements, in the ab- 

 sence of any food substance in the month, are sufficient to 

 transitory inhibition of the gastric tonus a receptivi 



