ON HUNGER AND THIRST 453 



eventuated by natural selection, and been determined with 

 the intention that its gratification might always be safe- 

 guarded by at least the local presence and supervision of 

 one special sense, and that that sense, moreover, should 

 be specially adapted to meet the special wants necessitated 

 by such a situation. 



The feeling of thirst is, thus, an index of liquid 

 requirements, exercised physiologically on behalf of local 

 and general systemic and sympathetic needs, and a regu- 

 lator of the quantity and quality of the liquid, as well as 

 the manner and method of its supply ; hence the necessity 

 for understanding aright, and following at all times its 

 true meanings and purposes. 



Hunger, in like manner, primarily manifests itself 

 locally, and secondarily more generally and indefinitely ; 

 locally it is experienced in the gastric region as a feeling 

 of regional vacuity or more or less vague faintness, or 

 " a gnawing void," and a more or less pronounced craving 

 for food, while generally there may synchronise with this 

 a feeling of declining tone and strength. Is this feeling, 

 like the feeling of thirst, localised by anatomical and func- 

 tional conditions ? We think so. Why ? Because it 

 occurs at the seat of the first great digestive procedure, 

 and is usually realised when the contents of the stomach 

 have been removed by absorption, or passed into the 

 small intestine, at which time the gastric juice is allowed 

 to impress the gastric wall, and the nervature distributed 

 therein, and so to indicate that, for the time being, gastric 

 digestion has been completed, and that there is a coming 

 necessity for the renewal of digestive material for the 

 satisfaction of the feeling. This feeling may be regarded 

 as of the greatest functional value in the economy of 

 nutrition and organic or formative activity, inasmuch as 

 it affords an index of the nature and quantity of the 

 required ingesta, and then ceases to send its messages of 

 demand as soon as its requirements are met and security 

 for the continuity of the nutritive process maintained. 



Thus, like thirst, hunger may be regarded as a cry, 

 or warning, to the economy that solid matter or food is 

 required for organic purposes if the processes of life are 

 to continue. It may, therefore, be understood as largely 



