HUNGER. 559 



regarded as the agents of this transmission; and it has been affirmed 

 by Baglivi, Valsalva, Haller, Dumas, Legallois, Chaussier, and others, 

 that if they be divided in the neck, although the stomach may be 

 favourably circumstanced, in other respects, for the developement of the 

 impression of hunger, and the encephalon for its reception, there is no 

 sensation ; but MM. Leuret and Lassaigne, 1 Dr. John Reid, 2 Nasse, 3 

 and Longet, 4 deny, that such effect follows the division of these 

 nerves; and the first gentlemen affirm, that horses have eaten as usual, 

 and apparently with the same appetite, after they had removed several 

 inches of the pneumogastric nerves; and even continued to eat after 

 the stomach was filled. To these experiments we shall have occasion 

 to refer hereafter. They by no means, however, exhibit that this in- 

 ternal sensation differs in its essence from others. 



A difficulty, which the physiologist has always felt, concerns the 

 precise nature of the action of impression. Its seat is clearly in the 

 stomach. This was shown incontestably by a case of fistulous opening 

 into the organ, which fell under the care of Dr. Beaumont, and to 

 which there will be frequent occasion to refer. When the subject of 

 this case was made to fast until his appetite was urgent, it was imme- 

 diately assuaged by feeding him through the aperture. To the stomach, 

 indeed, all our feelings refer the sensation. It is dependent upon some 

 modification occurring in the very tissue of the viscus; and in the 

 nerves, which, as has been shown, are the sole agents in all phenomena 

 of sensibility. These nerves are spread over the stomach, so that the 

 precise seat of the impression cannot be as accurately defined as in the 

 case of the organs of external sense. Moreover, the nerves of the 

 stomach proceed from two essentially different sources, the eighth 

 pair, and great sympathetic. The question consequently arises: on 

 which of these is the impression made ? The results of the experiment 

 of cutting the eighth pair in the neck would appear to decide in favour 

 of the former. 



As to the proximate or efficient cause of hunger, we cannot expect 

 to arrive at any satisfactory conclusion. It is a sensation; and, like 

 all sensations, inscrutable. Theories, however, as on all obscure topics, 

 have been numerous, and these have generally been of a mechanical or 

 a chemical nature. Some have attributed it to the mechanical friction 

 of the parietes of the stomach against each other, in consequence of its 

 contraction; in which state, they affirm, the mucous coat is rugous, and 

 its papillae and follicles prominent. It is manifest, however, from the 

 structure of the organ, that no such friction can take place. Yet this 

 view was embraced by Haller. 5 Dr. Fletcher 6 ascribes it to a kind of 

 permanent though partial contraction of the muscular fibres of the 

 stomach; "not that alternate general contraction and relaxation, 



1 Recherches Physiologiques et Chimiques pour servir & THistoire de la Digestion, Paris, 

 1825. 



a Edinb. Med. and Surg. Journal, April, 1839, and art. Par Vagum, in Cyclop, of Anat. 

 and Physiol., Pt. xxviii., p. 899, Lond., April, 1847. 



3 Untersuchungen zur Physiologie und Pathologic, Bonn, 1835-6. 



4 Traite de Physiologie, ii. 342, Paris, 1850. 



5 Element. Physiol., lib. xix., sect. 2, 12, Bern., 1764. 



6 Rudiments of Physiology, Part iii., by Dr. Lewins, p. 73, Edinb., 1837. 



