THE NATURE OF HUNGER 307
Since the lower end of the oesophagus, as well as the stomach, con- tracts periodically in hunger, the reference of the sensation to the sternum by the ignorant persons questioned by Schiff was wholly nat- ural. The activity of the lower oesophagus also explains why, after the stomach has been removed, or in some cases when the stomach is dis- tended with food, hunger can still be experienced. Conceivably the in- testines also originate vague sensations by their contractions. Indeed the final banishment of the modified hunger sensation in the patient with duodenal fistula, described by Busch, may have been due to the lessened activity of the intestines when chyme was injected into them.
The observations recorded in this paper have, as already noted, nu- merous points of similarity to Boldireff's observations on the periodic activity of the alimentary canal in fasting dogs. Each period of activ- ity, he found, comprised not only wide-spread contractions of the diges- tive canal, but also the pouring out of bile, and of pancreatic and in- testinal juices rich in ferments. Gastric juice was not secreted at these times; when it was secreted and reached the intestine, the periodic ac- tivity ceased. 46 What is the significance of this extensive disturbance? Eecently evidence has been presented that gastric peristalsis is depend- ent on the stretching of gastric muscle when tonically contracted. 47 The evidence that the stomach is in fact strongly contracted in hunger — i. e., in a state of high tone — has been presented above. 48 Thus the very condition which causes hunger and leads to the taking of food is the condition, when the swallowed food stretches the shortened muscles, for immediate starting of gastric peristalsis. In this connection the re- cent observations of Haudek and Stigler are probably significant. They found that the stomach discharges its contents more rapidly if food is eaten in hunger than if not so eaten. 49 Hunger, in other words, is normally the signal that the stomach is contracted for action; the un- pleasantness of hunger leads to eating; eating starts gastric secretion, distends the contracted organ, initiates the movements of gastric diges- tion, and abolishes the sensation. Meanwhile pancreatic and intestinal juices, as well as bile, have been prepared in the duodenum to receive the oncoming chyme. The periodic activity of the alimentary canal in fasting, therefore, is not solely the source of hunger pangs, but is at the same time an exhibition in the digestive organs of readiness for prompt attack on the food swallowed by the hungry animal.
46 Boldireff, loc. cit., pp. 108-111.
47 Cannon, this journal, 1911, XXIX., p. 250.
48 The "empty" stomach and oesophagus contain gas (see Hertz, Quarterly Journal of Medicine, 1910, III., p. 378; Mikulicz, " Mittheilungen aus dem Grenzgebieten der Medicin und Chirurgie," 1903, XII., p. 596). They would naturally manifest rhythmic contractions on shortening tonically on their content.
49 Haudek and Stigler, Archiv fur die gesammte Physiologie, 1910, CXXXIIL, p. 159.