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II. SPECIAL PHYSIOLOGY. 



CHAP. I. 



HUNGER, THIRST, AND FOOD. 



THE solid and fluid substances, taken into the mouth to repair 

 the losses of the system, are termed food and drink; or both are 

 comprised under the word food. 



The desire for the former is called hunger or appetite, and for 

 the latter, thirst. 



" Some ascribe hunger to an uneasiness arising in the stomach 

 from its being empty and unoccupied ; others, to the mutual 

 friction of its rugae ; others, not only to the stimulus of its fluids, 

 now secreted in abundance, of the saliva and gastric juice, but 

 to an acrimony which they acquire when food is not taken in 

 proper time." 



If hunger arise from merely a sense of vacuity in the stomach, 

 why should it be increased by the application of cold to the sur- 

 face, and instantly by the deglutition of cold liquids, &c. ? 



The explanation by friction of the rugae is equally unsatisfac- 

 tory ; because the friction of these, if it does really occur, cannot 

 be greater than the friction of the stomach against its contents 

 immediately after a meal, when the organ is in great action, but 

 at which time hunger does not exist. 



Nor can the presence of the gastric juice explain the matter: 

 because, as every one knows, no sensation arises in any other 

 organ, which is not excrementory, from the peculiar stimulus of 

 its natural fluid, and I presume that this is the stimulus intended, 

 for the mechanical stimulus, from the bulk of tfye gastric juice, 

 occurs equally from the presence of food, which does not excite 

 hunger ; because, if the hungry stomach is evacuated by vomiting, 

 as in sea-sickness, the appetite, when the sickness has ceased, is 

 even greater than before ; and because hunger often ceases after 

 a time, though the gastric juice still remains in the stomach, and 

 is probably more abundant than ever. 



E 



