DEMAND FOR ALIMENT. SENSE OF HUNGER. 481 



can be sustained only by a large supply of highly nutritious food. The 

 mother who has to furnish the daily supply of milk, which constitutes the 

 sole support of her offspring, needs an unusual sustenance for this purpose. 

 And there are states of the system, in which the solid tissues seem to possess 

 an unusual tendency to decomposition, and in which an increased supply of 

 aliment is therefore required. This is the case, for example, in Diabetes ; one 

 of the first symptoms of which disease is the craving appetite, that seems as 

 if it would be never satisfied. And there can be no doubt that, putting aside 

 all the other circumstances which have been alluded to, there is much differ- 

 ence amongst individuals, in regard to the rapidity of the changes which their 

 organism undergoes, and the amount of food consequently required for its 

 maintenance. 



636. The want of solid aliment is indicated by the sensation of Hunger ; 

 and that of liquid by thirst. The former of these sensations is referred to 

 the stomach ; and the latter to the fauces : but although certain conditions of 

 these parts may be the immediate cause of the sensations in question, they 

 are really indicative of the requirements of the system at large. For the in- 

 tensity of the feelings bears no constant relation to the amount of solid or 

 liquid aliment in the stomach ; whilst, on the other hand, it does correspond 

 with the excess of demand in the system, over the supply afforded by the 

 blood ; and it is caused to abate by the introduction of the requisite materials 

 into the circulating fluid, even though this be not accomplished in the usual 

 manner by the ingestion of food into the stomach. 



637. That the sense of Hunger, however, is immediately dependent upon 

 some condition of the Stomach, seems to follow from the fact, that it is abated, 

 if not arrested, by section of the Par Vagum ( 412) ; and that it may be 

 temporarily alleviated, by introducing into the digestive cavity, matter which 

 is not alimentary. Of the precise nature of that condition, however, we have 

 no certain 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 a renewal of the uneasy feeling; and this emptiness may continue 

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

 out a return of desire for food. It 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 the production of it is 

 stimulated by the irritation of its secreting follicles. By Dr. Beaumont it is 

 thought, that the distension of these follicles with the secreted fluid is the 

 proximate cause of hunger; but there is no more reason to believe that the 

 secretion of Gastric fluid is accumulating during the intervals when it is not 

 required, than there is in regard to Saliva, the Lachrymal fluid, or any other 

 secretions, which are occasionally poured out in large quantities under the in- 

 fluence of a particular stimulus; and, moreover, it is difficult to imagine how 

 mental emotion, or any impression on the nervous system alone (which is 

 able, as is well known, to dissipate the keenest appetite in a moment), can re- 

 lieve such distension. 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 secretion, 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 Par Vagum. When food is in- 

 troduced into the stomach, the act of secretion is directly excited ; the capil- 

 lary vessels are gradually unloaded ; and the immediate cause of the impres- 

 sion on the par vagum is withdrawn. By the conversion of the alimentary 



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