512 DIGESTION 



stimuli that may set up impulses traveling by the extrinsic nerves 

 to the stomach are convoyed by the nerves of sense or are of psy- 

 chic origin. Stimulation of the gustatory end organs in the mouth, as 

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

 and a diminution or disappearance of the hunger contractions. Even the 

 chewing of indifferent substances, such as paraffin, suffices to produce 

 distinct inhibition, unless in a case in which the contraction has passed 

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

 sence of any food substance in the mouth, are sufficient to produce a 

 transitory inhibition of the gastric tonus a receptive relaxation of the 

 stomach, as it has been aptly called. The diminution in tonus and 

 hunger contractions in these various ways is accompanied by a diminu- 

 tion in the hunger pains. 



Afferent nerve stimulation affecting the hunger contractions may also originate in 

 the stomach mucosa itself, as has been shown by Carlson on his patient by introducing 

 the various substances to be tested through a tube into the stomach. A glassful of 

 cold water introduced in this way inhibits the tonus and the hunger contractions for 

 from three to five minutes unless these are severe, this inhibition being followed by no 

 augmentation either of the tonus or of contractions. Ice-cold water has a greater 

 effect than water at body temperature. This result is somewhat different from that 

 which most men experience as the result of drinking a glass of cold water. 



Weak acids of strengths varying up to that found present in the gastric juice itself 

 0.5 per cent cause a marked inhibition of the hunger movements, but this inhibition 

 does not persist until all the acid has escaped from the stomach or been neutralized, 

 which explains why hunger contractions should still occur when an acid secretion is 

 present in the stomach, as in starvation. Normal gastric juice itself produces an in- 

 hibition, which is no doubt dependent upon the acid which it contains, and it is prob- 

 able that, at the same time that it leads to inhibition of the hunger contractions, the 

 acid initiates peristalsis of the pyloric region (see page 487). Weak alkaline solu- 

 tions have no greater effect on the hunger contractions than an equal volume of water. 

 Weak solutions of local anesthetics, such as phenol or chloretone, are without effect. 



With regard to alcoholic beverages interesting results were obtained. Wine, beer, 

 brandy, and diluted pure alcohol inhibit both the tonus and the contractions. The 

 duration of this inhibition varies directly with the quantity of the beverage intro- 

 duced into the stomach and with its alcohol percentage. These observations are ap- 

 parently not in harmony with the experience of most men that the taking of alcoholic 

 beverages serves to awaken or increase the appetite, the difference being no doubt due 

 to the fact that appetite and hunger contractions of the stomach are not dependent on 

 each other, appetite being, as we have seen, a complex psychic affair, whereas the 

 hunger contractions depend upon a local mechanism in the stomach wall itself. 



As the inhibition produced in one or other of these ways passes off, 

 the hunger contractions are resumed at their previous intensity and not 

 in an augmented form. From the promptness of the inhibition, it would 

 appear that the stomach contractions are affected, not reflexly through 

 the central nervous system or by changes in the chemical composition 

 of the blood, but by a direct action on the neuromuscular mechanism 



