262 THE HUMAN MECHANISM 



but when the cardiac pouch is again empty, the inhibiting 

 check is removed and the automatic " beats " become quite 

 powerful. These contractions start impulses up the sensory 

 nerves of the stomach, and these impulses excite in our con- 

 sciousness sensations of hunger. Often the " beats " occur 

 in rhythmic periods, a group of strong contractions alter- 

 nating with groups of weak contractions or even total 

 quiescence. In this case we have the " griping " hunger 

 pangs coincident with the strong contractions. In certain 

 abnormal conditions the presence of food in the stomach 

 fails to exert its inhibiting effect and we have a continual 

 " gnawing " hunger. 



Thirst is aroused by the dryness of the mouth and throat, 

 probably by the reduction of the amount of water in cells 

 and tissues of this organ. 



Hunger and thirst are definite sensations, as truly adapted 

 to guide us in the choice of food as sight is adapted to 

 picture to us the world in which we live. So long as the 

 body is normally occupied and healthy they may usually 

 be trusted; but there are abnormal conditions of sedentary 

 life, in the midst of a superabundance of tempting food, 

 when they become less trustworthy, and in some forms of 

 dyspepsia the sensation of hunger is never absent, no matter 

 how often one eats. In such cases the very effort to satisfy 

 hunger only aggravates disease. Conditions of this sort 

 should not prevail if proper attention be paid to the general 

 hygienic conduct of life. Broadly speaking, appetites, like 

 fire and dynamite, are good servants but bad masters. 



