OF HUNGER AND THIRST STARVATION. 121 



tain knowledge. It is easy to prove that many of the causes which have 

 been assigned for the sensation, are but little, if at all, concerned in pro- 

 ducing it. Thus, mere emptiness of the stomach cannot occasion it; since, 

 if the previous meal have been ample, the food passes from its cavity some 

 time before the uneasy feeling is renewed; and this emptiness may continue 

 (in certain disordered states of the system) for many hours or even days, 

 without a return of desire for food. Besides, the stomach may be filled with 

 food, and yet Hunger may be intensely felt, if, from disease of the pylorus 

 or any other cause, there be an obstacle to the passage of the aliment into 

 the intestine, and to the completion of the processes of chylificatiori and 

 absorption, so that the system needs that which the digestive apparatus is 

 unable to provide for it. Again, the sense of Hunger cannot be due, as 

 some have supposed, to the action of the gastric fluid upon the coats of the 

 stomach themselves ; since this fluid is not poured into the stomach, except 

 when its production is stimulated by the irritation of the secreting follicles. 

 Nor is it conveyed through the pneumogastrie nerves, since, as shown by 

 Dr. John Reid, 1 after section of these nerves animals take food with no less 

 avidity than previously; indeed, the sense of satiety rather than that of 

 Hunger seems to be abolished, the animals often continuing to gorge them- 

 selves with food long after the stomach has been adequately filled. It may, 

 perhaps, be a more probable supposition, that there is a certain condition of 

 the Capillary circulation in the Stomach, which is preparatory to the secre- 

 tion, and which is excited by the influence of the Sympathetic nerves, that 

 communicate (as it were) the wants of the general system. This condition 

 may be easily imagined to be the proximate cause of the sensation of hunger, 

 by acting on the nervous centres. When food is introduced into the 

 stomach, the act of secretion is directly excited ; the capillary vessels are 

 gradually unloaded; and the immediate cause of the impression on the 

 nervous system is withdrawn. 2 By the conversion of the alimentary mat- 

 ter into materials fit for the nutrition of the system, the remote demand 

 also is satisfied ; and thus it is, that the condition of the stomach just refer- 

 red to, is permanently relieved by the ingestion of substances that can serve 

 as food. But if the ingested matter be not of a kind capable of solution 

 and assimilation, or the digestive apparatus cannot effect its preparation, 

 the feeling of hunger is only temporarily relieved, and soon returns in 

 greater force than before. The theory here given seems reconcilable with 

 all that has been said of the conditions of the sense of Hunger; and par- 

 ticularly with what is known of the effect produced upon it by nervous im- 

 pressions, which have a peculiar influence upon the capillary circulation. 

 It also corresponds exactly with what we know of the influence of the 

 nervous system, and of mental impressions, upon other secretions (chapter 

 xvii ). 



76. The sense of Hunger, like other sensations, may not be taken cogni- 

 zance of by the mind, if its attention be strongly directed towards other 

 objects ; of this fact, almost every one engaged in active operations, whether 

 mental or bodily, is occasionally conscious. The nocturnal student, who 

 takes a light and early evening meal, and after devoting himself to his pur- 

 suits for several hours uninterruptedly, retires to rest with a wearied head 

 and an empty stomach, but without the least sensation of hunger, is fre- 

 quently prevented from sleeping by an indescribable feeling of restlessness 

 and deficiency ; and the introduction of a small quantity of food into the 



1 Phys. Anat. and Path. Researches, pp. 234-239. 



2 These views seem lu be confirmed by the observations of M. Bernard on the 

 condition of the gastric follicles during the intervals of their functional activity. 



9 



