SENSE ORGANS AND SENSATIONS 261 



suffering in the hope that he will soon be better and that the 

 trouble will " cure itself." Sometimes, of course, it does cure 

 itself ; but sometimes it does not ; and remediable disease 

 has too frequently been allowed to run on in this way until 

 some vital spot is attacked or the trouble has become too 

 grave for medical skill to overcome. Many diseases, like a 

 fire, may be extinguished at the start, but if not attended to, 

 grow rapidly into a conflagration beyond control. Pain is 

 one of the most trustworthy warnings that attention to the 

 mechanism itself or to our operation of it is necessary; and 

 we have no right, either for our own sake or that of our 

 friends, to neglect its warnings. While there are times when 

 it is an act of heroism to endure suffering and to keep the 

 knowledge of it to one's self, there are other times when to 

 do this is not only foolish but wrong. 



25. Hunger and thirst. No account of the physiology of 

 sensations would be complete without some reference to 

 those very common experiences of life hunger and thirst. 

 We have already spoken of them as sensations which are 

 referred to the body and never to external objects, thirst 

 usually being referred to the mouth and throat, and hunger 

 frequently to the stomach ; but hunger and even thirst may 

 sometimes affect us as sensations coming from the body as 

 a whole, in which case they are usually indistinguishable 

 from certain forms of general fatigue. 



Hunger is excited by automatic rhythmic contractions of 

 the musculature of the cardiac end of the stomach. The 

 stomach, like the heart, executes rhythmic contractions, and 

 we may speak of the " beat " of the stomach just as we 

 speak of the " beat " of the heart, although each stomach 

 contraction is much slower than those of the heart. When 

 food is in the stomach, these contractions or " beats " are 

 inhibited in the cardiac end or else are reduced to very in- 

 significant proportions, and we have the inactive condition 

 of this portion of the stomach described in Chapter VIII ; 



