508 DIGESTION 



itself the tonus has become conspicuous, and the stronger hunger con- 

 tractions usually begin to appear. Superimposed upon those of the 

 tonus rhythm, hunger pangs may appear in man when the stomach still 

 contains traces of food. 



By studying the shadow of the outline of the stomach produced by 



Fig. 167. Tracing of the tonus rhythm of the stomach (man) three hours after a meal. (From 



Carlson.) 



having a person or animal swallow two balloons, one inside the other 

 and with a paste of bismuth subnitrate between them, it has been ob- 

 served that the weaker type of hunger contraction begins as a con- 

 striction involving the cardiac end of the stomach, and moving toward 

 the pyloric end as a rapid peristaltic wave. When the contractions are 



Fig. 168. Tracings from the stomach during the culmination of a period of vigorous gastric hunger 

 contractions. One-half original size. (From Carlson.) 



very vigorous, this wave spreads so rapidly over the stomach that it is 

 difficult to determine whether it really occurs as a very rapid peristalsis 

 or as a contraction involving the fundus as a whole. These contractions 

 resemble very closely the movements that have sometimes been observed 



