350 SPECIAL PHYSIOLOGY. 



water, or even taking draughts of neutral vegetable salts, such as 

 seidlitz powders. It is also produced by hot condiments, and by strong 

 alcoholic beverages. It is particularly and distressingly noticeable in 

 cases of hemorrhage after gunshot wounds or other extensive injuries, 

 and in all cases of fever. The intense thirst experienced by ship- 

 wrecked sailors, and by criminals subjected to the torture of thirst, is 

 accompanied by burning pains and sufferings, more difficult to bear 

 even than those induced by prolonged starvation, and ending in de- 

 lirium and mania. Thirst is more immediately and successfully 

 quenched by water than by any other fluid. It is water which the 

 system absorbs from the blood, in thirst, the tissues, as well as the 

 secretions, requiring it ; and the introduction or imbibition of this fluid 

 is the natural remedy for this sensation. 



The sensations of appetite and hunger, the former of which is pleas- 

 ant, and the latter painful, are by some regarded as chiefly muscular 

 sensations. They are referred to the stomach, in the same way as 

 thirst is referred to the mouth ; but, like the latter sensation, they 

 would seem to depend on a general condition of the system, and per- 

 haps essentially on some state of the blood. The muscles of mastica- 

 tion are said to participate in the sensation of appetite; and a flow of 

 saliva is excited by it. It may be supposed that the nerves of the 

 stomach convey the sensations proper to that state of the system in- 

 duced by fasting, more readily than the nerves of any other part of 

 the body. Several theories have been suggested to explain the gnaw- 

 ing feeling of hunger, which is even more decidedly felt in the stomach 

 than appetite. Some physiologists, offering a mechanical explanation, 

 have thought that it is owing to the rubbing together of the sides of 

 the empty stomach ; but this explanation is opposed to the facts, that 

 the stomach may be empty without hunger being felt, and that, in the 

 fasting condition, when hunger is experienced, the walls of the stomach 

 are quiescent. As a chemical theory of the cause of hunger, it has 

 been suggested, that it depends on irritation excited by unused gastric 

 juice; but no gastric juice is secreted during fasting. A physiological 

 explanation consists in supposing that the feeling of hunger is owing 

 to a turgescence of the bloodvessels of the mucous membrane of the 

 stomach; but this membrane is pale when the stomach is empty; 

 indeed, the secretion of gastric juice takes place rapidly, and the 

 membrane then suddenly becomes red. That the sensation of hunger 

 depends partly on some condition of the stomach itself, is shown by 

 the fact, that it may be allayed by the introduction into that cavity of 

 almost, or perfectly indigestible substances, such as sawdust, or clay ; 

 even when the stomach is filled with digestible substances, the feeling 

 of hunger is relieved before any material quantity of digested food 

 can have been absorbed. Hunger is not, however, so speedily relieved 

 as thirst. On the other hand, that it depends mainly on a peculiar 

 condition of the system, is shown by the experiments of injecting nu- 

 trient substances, in the form of enemata, or into the blood itself, 

 either of which is followed by a cessation of the feeling of hunger. 

 The nerves distributed to the stomach, which are concerned in this 

 sensation, must either be derived from the pneumogastric, or from the 



