CHAPTER LIV 

 HUNGER AND APPETITE 



Hunger and appetite are distinct and separate sensations, the former 

 being definitely correlated with contractions of the empty stomach, and the 

 latter, a complex of sensory impressions integrating in the nervous system 

 along with memory impressions of the sight, taste, and smell of palatable 

 food. Appetite is therefore a highly complex nervous integration, whereas 

 hunger is a much simpler process. It is particularly with hunger that 

 we shall concern ourselves at present. 



When a thin-walled rubber balloon of proper size is placed in the 

 stomach and connected by a rubber tube with a water, bromoform or 

 chloroform manometer (made of wide glass tubing 1.5 cm. in diameter 

 and provided with a suitable float on the free limb) a tracing may be 

 taken of the movements of the stomach. For use on man the capacity of 

 the balloon should be from 75 to 150 cubic centimeters. The record thus 

 obtained when the balloon is placed in the empty stomach of a normal 

 person shows four types of wave. Two of these may be discounted, 

 being due to the arterial pulse and the respiratory movements. The 

 third is known as the tonus rhythm, and is caused by tonic contractions 

 of the fundus of the stomach of varying amplitude. The periods of tonus in- 

 crease during the powerful rhythmic contraction to be immediately 

 described. While these changes in tone are occurring, no subjective sen- 

 sation of hunger is experienced. (See Fig. 167.) 



The fourth and most significant type consists of powerful rhythmic 

 contractions, alternating with periods of quiescence. These contrac- 

 tions occupy a period of about twenty seconds, and are superimposed 

 upon the tonus rhythm. They gradually increase in amplitude and fre- 

 quency; and, in the case of young and vigorous persons, may gradually 

 pass into a condition of incomplete tetanus, after which they suddenly 

 subside, leaving only a faint tonus rhythm. These rhythmic contrac- 

 tions are definitely associated with the sensation of hunger, and are 

 more marked the more intense the sensation. When tetanus occurs 

 the hunger sensation is continuous, but it instantly disappears when 

 the tetanus gives place to relaxation. When the contractions are com- 

 paratively feeble, the length of the period during which they occur is 



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