HUNGER AND APPETITE 513 



in the stomach walls, and it is important to bear in mind that the 

 inhibitory effects 011 the stomach contractions of the fundus may proceed 

 quite independently of the changes in the pyloric region that are con- 

 cerned with the mechanical processes of digestion. After one or both 

 of the extrinsic nerves of the stomach were severed in dogs, a certain 

 degree of inhibition could still be induced by the above methods, indicat- 

 ing that, although section of the extrinsic nerves depresses the inhibitory 

 reflex, it does not abolish it. 



Various mitigations of the hunger contractions have been discovered. 

 Smoking: has this effect, and compression of the abdomen by tightening 

 the belt also inhibits the contractions provided they are not of marked 

 intensity. Considerable muscular exercise, such as brisk walking or 

 running, causes inhibition, which usually persists until after the exer- 

 cise is discontinued. When the tonus and contractions return, in this 

 case, they seem to be somewhat more pronounced. Application of cold 

 to the surface of the body as by placing an ice pack on the abdomen 

 or taking a cold douche, procedures which are well known to induce 

 increased neuromuscular tonus, in general causes an inhibition of the 

 gastric tonus and hunger contractions, the degree of which is roughly 

 proportional to the intensity of the stimulation. There is certainly never 

 an increase in the gastric tonus or hunger contractions. If such stimula- 

 tion is maintained, the inhibitory effects on the stomach gradually 

 diminish, even though the individual be shivering intensely. 



With regard to the nerve centers concerned in these phenomena, little that is definite 

 is known. The sensory nuclei of the vagus nerve in the medulla must be considered 

 as the primary hunger center, and through this center, not only influences affecting the 

 stomach contractions, but also those associated with the hunger sensations, must be 

 mediated. It Avould appear from observations on the hunger behavior of decerebrate 

 animals that there can be no hunger center located on the cerebral cortex itself, for 

 such animals exhibit practically the same hunger effects as normal animals. It is in- 

 teresting to note that, at least in the case of decerebrate pigeons, this hunger behavior 

 entirely disappears on removal of the optic thalami, where important nerve centers hav- 

 ing to do with the bodily responses of the animal to hunger impulses would therefore 

 appear to be located. These observations support the suggestion that has been made 

 by several neurologists that the sense of pain is located somewhere in the thalamic 

 region. 



Concerning the influence of psychic states, Carlson says that in his 

 own case the hunger contractions became weaker and the intervals 

 between them greater when he was suddenly awakened during his 

 fast and saw two of his friends partaking at his bedside of a "feast of 

 porterhouse steak with onions, potatoes, and a tomato salad." These 

 results are no doubt due to local inhibition dependent upon the psychic 

 secretion of appetite gastric juice. When no such juice is produced, 

 the sight and smell of good food does not appear to affect materially 



