CHAPTER LVI 



HUNGER, APPETITE AND THIRST 



The sensations of hunger and appetite are due to different causes, the 

 former being definitely correlated with contraction of the empty stomach, 

 and the latter being a complex of sensations operating in the nervous 

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

 palatable food. Appetite is therefore a highly complex nervous integra- 

 tion, whereas hunger is a much simpler process. It is particularly with 

 hunger that we shall concern ourselves at present. 



Hunger 



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 (Fig. 166). 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 contractions 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 pass into 

 a condition of incomplete tetanus, after which they suddenly subside, 

 leaving only a faint tonus rhythm. The rhythmic contractions are defi- 

 nitely associated with the sensation of hunger, and are more marked 

 the more intense the sensation is. When tetanus occurs the hunger sen- 

 sation is continuous, but it instantly disappears when the tetarlus gives 

 place to relaxation. 



50G 



