HUNGER AND THIRST. 29 1 



possess it, and by continual practice may become a habit. 

 There are cases also of rare occurrence in which persons] 

 habitually swallow their food hastily, and nearly unmasti- 

 cated, and then at their leisure regurgitate it, piece by 

 piece, into their mouth, remasticate, and again swallow it, \ 

 exactly as is done by the ruminant order of Mammalia. 



Influence of the Nervous System on Gastric Digestion. 



This influence is manifold ; and is evidenced, 1st, in the 

 sensations which induce to the taking of food ; 2nd, in the 

 secretion of the gastric fluid ; $rd, in the movements of the 

 food in and from the stomach. 



The sensation of hunger is manifested in consequence of 

 deficiency of food in the system. The mind refers the 

 sensation to the stomach ; yet since the sensation is relieved 

 by the introduction of food either into the stomach itself, 

 or into the blood through other channels than the stomach, 

 it would appear not to depend on the state of the stomach 

 alone. This view is confirmed by the fact, that the divi- 

 sion of both pneumogastric nerves, which are the principal 

 channels by v, hich the mind is cognisant of the condition 

 of the stomach, does not appear to allay the sensations of 

 hunger. 



But that the stomach has some share in this sensation 

 is proved by the relief afforded, though only temporarily, 

 by the introduction of even non-alimentary substances into 

 this organ. It may, therefore, be said that the sensation 

 of hunger is derived from the system generally, but chiefly 

 from the condition of the stomach, the nerves of which, 

 we may suppose, are more affected by the state of the in- 

 sufficiently replenished blood than those of other organs 

 are. 



The sensation of thirst, indicating the want of fluid, is 

 referred to the fauces, although, as in hunger, this is 

 merely the local declaration of a general condition existing 

 in the system. For thirst is relieved for only a very short 



u 2 



