HUNGER AND APPETITE 479 



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

 inhibitory effects on 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 

 would 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 interesting 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 having to do with 

 the bodily responses jof 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 



