140 ALIMENTATION 



resorted to when starvation had become imminent ; suffice it to say that 

 the extremity of hunger or of thirst, like the sense of impending suffoca- 

 tion, is a demand on the part of the system so imperative that it must 

 be satisfied if within the range of possibility. 



When the system is suffering from defective nutrition, as after pro- 

 longed abstinence or during convalescence from diseases attended with 

 defective assimilation, the mere filling of the stomach produces a sen- 

 sation of repletion of this organ, but the sense of hunger is not re- 

 lieved ; but if, on the other hand, the nutrition is active and sufficient, 

 the stomach frequently is entirely empty for a considerable time without 

 the development of the sense of hunger. The appetite is preserved and 

 hunger is felt by persons who suffer from extensive organic disease of 

 the stomach, and the sensation occasionally has been relieved by nutri- 

 tious enemata or by injections into the veins. It is certain that appetite 

 and the sense of hunger are expressions of a want on the part of the 

 organism, referred by the sensations to the stomach, but really existing 

 in the general system. This can be completely satisfied only by the 

 absorption of digested alimentary matters by the blood and their assimi- 

 lation by the tissues. 



The sense of hunger undoubtedly is appreciated by the cerebrum, 

 and it has been a question whether there be any special nerves that 

 convey this impression to the encephalon. The nerve which naturally 

 would be supposed to have this office is the pneumogastric ; but not- 

 withstanding certain observations to the contrary, it has been shown 

 that section of both these nerves by no means abolishes the desire for 

 food. It has been observed that dogs eat, apparently with satisfaction, 

 after section of the glosso-pharyngeal and lingual nerves. It has been 

 thought, also, that the sensation of hunger is conveyed to the brain 

 through the sympathetic system. Although there are various consid- 

 erations that render this somewhat probable, it is not apparent how it 

 can be demonstrated experimentally. It is undoubtedly the sympathetic 

 system of nerves that presides specially over nutrition ; and hunger, 

 which depends upon deficiency of nutrition, is certainly not conveyed to 

 the brain by any of the cerebro-spinal nerves. 



Thirst is the peculiar sensation that leads to the ingestion of water. 

 In its moderate development, this usually is an indefinite feeling, accom- 

 panied by more or less dryness and heat of the throat and fauces, and 

 sometimes, after the ingestion of a quantity of very dry food, by a 

 sensation referred to the stomach. When the sensation of thirst has 

 become intense, the immediate satisfaction following the ingestion of a 

 liquid, particularly water, is very great. Thirst is very much under the 

 influence of habit ; some persons experiencing a desire to take liquids 



