754 SPECIAL SOMATIC AND VISCERAL RECEPTORS 



pouring of gastric juice. A third hypothesis is that hunger is due 

 to the stimulation of certain afferent nerves in the stomach by the 

 contraction of its musculature. In support of this view might be men- 

 tioned the contracted state of the empty stomach, the periodic peri- 

 staltic waves passing over it, the aboUtion of this sensation after the 

 introduction of indigestible substances, and the rumbling gastric noise 

 produced when this sensation is experienced. Cannon and Washburn 

 have proved that the sensation of hunger occurs simultaneously with 

 increases in intragastric pressure. In nervous persons, however, and 

 especially in women, loud rumbling noises are frequently heard 

 without being associated with this sensation. 



Carlson^ has repeated these observations upon a man with a 

 gastric fistula established after the occlusion of the esophagus by a 

 cicatrix. It is stated that there is a fairly close correspondence be- 

 tween the duration of the contractions and the duration of the sub- 

 jective sensation of hunger. A similar relationship was noted between 

 the intensity of this sensation and the strength and rapidity of develop- 

 ment of the contractions. Moreover, while a distinct sensation of 

 hunger could be produced by suddenly inflating a balloon placed in 

 the stomach, it could not be evoked by tactile stimulation of the gas- 

 tric mucosa. The peripheral genesis of this sensation, therefore, 

 seems established, although no definite data have been obtained regard- 

 ing the nervous mechanism involved in it. 



Attention should also be called at this time to the continued sensa- 

 tion of hunger experienced by the diabetic patient which prompts him 

 to eat superfluous amounts of food. A similar condition frequently 

 results in persons whose lower intestine has been made to open through 

 the abdominal wall in order to relieve an, obstruction in the rectum or 

 neighboring parts (Carcinoma). Under this condition the pangs of 

 hunger are experienced even when the stomach is comfortably filled 

 with food. In view of these facts, it might be well to recognize two 

 types of hunger, namely, gastric hunger which is present normally, and 

 general or somatic hunger which is brought into play under unusual 

 conditions. 



Thirst. — The sensation of thirst is specifically referred to the 

 pharynx, unless there is a general scarcity of water, in which case this 

 local sensation is augmented by fatigue, anguish, pain and suffering. 

 In the first instance, the sensation is evoked in a circumscribed region 

 of the pharynx situated directly in the path of the currents of air ebb- 

 ing back and forth between the outside"*and the lungs. It is conceiva- 

 ble that the terminals of the glossopharyngeus nerve are specifically 

 adapted to perceive variations in the water content of the cells lining 

 this area, because thirst is experienced as soon as the latter becomes dry 

 and even at a time when the body as a whole is abundantly supplied 

 with water. A local moistening then suffices to give reHef without that 

 water is actually taken into the stomach. But, these lining cells may 

 1 Am. Jour, of Physiol., xxxi, 1912, 175. 



