HUNGER 199 



transport (Chap. XXVII.), there are certain definite movements of 

 the alimentary canal designated as peristaltic associated with the 

 forward transference of the contents of the canal. In the absence 

 of any content other than gaseous, the cavities of the stomach, 

 lower oesophagus and upper intestinal region, at least, are almost 

 obliterated. This wave of contraction precedes the sensation of 

 hunger and may be regarded as the cause of it. Carlson and his 

 students, who were fortunate in having a subject with a per- 

 manent gastric fistula, have confirmed Cannon's work and carried 

 it further. They have shown that the local contraction is a sign 

 of a general state. According to Carlson and Luckhardt the 

 blood of a fasting animal, if injected into the vein of a normal 

 animal, is capable of producing in the latter, contraction of the 

 gastric muscles, an effect which does not occur when the blood 

 of a well-fed animal is injected. 



The significance of this phenomenon is plain. In Cannon's 

 words : 



" The very condition which causes hunger and leads to the 

 taking of food is the condition, when the swallowed food stretches 

 the shortened muscles, for immediate starting of gastric peri- 

 stalsis. In this connection, the observations of Haudek and 

 Stigler are probably significant. They found that the stomach 

 discharges its contents more rapidly if food is eaten injiunger 

 than if not so eaten. Hunger, in other words, is normally the 

 signal that the stomach is contracted for action ; the unpleasant- 

 ness of hunger leads to eating, eating starts gastric digestion and 

 abolishes the sensation. Meanwhile the pancreatic and intestinal 

 juices as well as bile have been prepared in the duodenum to 

 receive the oncoming chyme. The periodic activity of the 

 alimentary canal in fasting, therefore, is not solely the source of 

 hunger pangs, but is at the same time an exhibition in the digestive 

 organs of readiness for prompt attack on the food swallowed by 

 the hungry animal." 



