474 DIGESTION 



resemble very closely the movements that have sometimes been observed 

 after a bismuth meal, and which have been thought by clinical observers 

 to indicate a hyperperistalsis of the stomach. The fundus is therefore 

 not entirely passive during digestion; for, although early in this act 

 there may be no evidence of contraction, yet the contractions of the tonus 

 rhythm may appear and become pronounced before the stomach is en- 

 tirely empty. In other words, the digestion contractions of the filled 

 stomach (see page 451) pass gradually over into the hunger contractions 

 of the empty organ. 



It appears that the stomach contractions produce the hunger sensa- 

 tions by causing stimulation of afferent nerve endings in the muscle 

 layers of the viscus. Mere pressure on the mucosa itself does not originate 

 such a sensation; thus, sudden distention of the balloon or rubbing the 

 mucosa with the closed end of a test tube, inserted through a gastric 

 fistula, was not found to cause any sensation of hunger, unless the stimulus 

 was so strong as to excite a contraction of the musculature of the stomach. 



It has been thought by some observers that, during hunger, contrac- 

 tions similar to those of the stomach also occur in the lower end of the 

 esophagus. It is believed by Carlson, however, that these contractions 

 are not at all responsible for the hunger sensation, although they may 

 give rise to a feeling that something has stuck in the esophagus. Con- 

 tractions of the intestine have also been observed in hunger, but it is doubt- 

 ful whether they have anything to do with the cause of the hunger 

 sensation. 



REMOTE EFFECTS OF HUNGER CONTRACTIONS 



It is well known that during hunger certain general subjective symp- 

 toms are likely to be experienced, such as a feeling of weakness and a 

 sense of emptiness, with a tendency to headache and sometimes even 

 nausea in persons who are prone to headache as a result of toxemic 

 conditions. Headache is likely to be more prounced or perhaps present 

 only in the morning before there is any food in the stomach. These 

 symptoms indicate that hunger contractions are associated with hyper- 

 excitability of the central nervous system, and it is of considerable 

 interest that objective signs of this association can be elicited. If the 

 knee-jerk be recorded along with a record of the gastric contractions, it 

 will be found that it is markedly exaggerated simultaneously with the 

 strong hunger contractions of the empty stomach, this augmentation 

 being greatest at the height of the stomach contractions, when the hun- 

 ger pangs are most intense, and falling off again to normal when these 

 disappear (Fig. 169). Further changes occurring during the hunger 



