MOVEMENTS OF THE ALIMENTARY CANAL. 725 



and Doyon* has confirmed this result in cases in which the move- 

 ments and tonicity of the stomach were first increased by the action 

 of pilocarpin and strychnin. Cannon, in his observations upon cats, 

 found that all movements of the stomach ceased as soon as the 

 animal showed signs of anxiety, rage, or distress. 



Hunger Contractions. After the stomach has been empty for 

 a certain time we experience sensations of hunger that are more 

 or less of a subpainful character and are, therefore, frequently 

 designated as "hunger-pains." These sensations appear and dis- 

 appear at irregular intervals until food is taken into the stomach. 

 Cannon and Washburn f first showed that these sensations appear 

 simultaneously with contractions of the stomach, and they sug- 

 gested that the hunger contractions cause the hunger-pains. 

 These particular movements have been investigated since by 

 Carlson J upon a man with a permanent gastric fistula. He finds 

 that when the hunger contractions are occurring they are inhibited 

 by chemical or mechanical stimulation of the gastric mucosa or 

 by the chewing or tasting of palatable food. The hunger contrac- 

 tions must constitute a variety of movements quite different in 

 mode of causation from the movements exhibited during gastric 

 digestion. Like the latter, however, they are essentially auto- 

 matic, that is to say, they continue when the extrinsic nerves are 

 severed and, therefore, are probably initiated and controlled 

 by the intrinsic nervous apparatus of the stomach. Carlson sug- 

 gests that the hunger contractions may involve primarily the 

 musculature of the fundic and cardiac region, while the contrac- 

 tions of digestion, as is known, are exhibited chiefly in the muscula- 

 ture at the pyloric end. 



Movements of the Intestines. The muscles of the small and 

 the large intestine are arranged in two layers, an outer longitudinal 

 and an inner circular coat, while between these coats and in the 

 submucous coat there are present the nerve-plexuses of Auerbach 

 and Meissner. The general arrangement of muscles and nerves is 

 similar, therefore, to that prevailing in the stomach, and in accor- 

 dance with this we find that the physiological activities exhibited 

 are of much the same character, only, perhaps, not quite so complex. 



Two main forms of intestinal movement have been distinguished, 

 the peristaltic and the pendular or rhythmic. 



Peristalsis. The peristaltic movement consists in a constriction 

 of the walls of the intestine, which, beginning at a certain point, 

 passes downward away from the stomach, from segment to segment, 

 while the parts behind the advancing zone of constriction gradually 



' "Archiv de physiologie normale et pathologique," 1895, p. 374. 



I Cannon and Washburn, "American Journal of Physiology," 29, 441, 1912. 



t Carlson, ibid., series of papers, vols. 31 to 34, 1912-1914. 



