HUNGER AND THIRST. 991 



sensations are all contributory to common sensation, and therefore 

 potentially possess the attribute with which all forms of common 

 sensation are intensely imbued, namely, " affective tone," — and physical 

 pain is stronger than physical pleasure. The relation of the stomach 

 to the " feeling of hunger " is a helpful instance. 



The prominent features of the "feeling "hunger are— (1) peculiar sensations, 

 referred to the epigastrium (stomach) ; (2) general " sinking " or " feeling of 

 weakness " ; (3) desire for food. Regarding the first the sensations are of an 

 ill-localised gnawing character, principally referred to the epigastrium but not 

 confined to that region, for the pharynx shares in them. The nature of the 

 stimulus provoking these local sensations is not clear. It is often said to be 

 " emptiness of the stomach." Introduction of food into the stomach rapidly 

 stops the feeling, even before much absorption of the taken food can have 

 occurred. Hunger is temporarily relieved by introducing non-nutritious 

 material into the stomach. It has been urged, on the other hand, that a 

 rabbit after twenty-four hours' abstinence is very hungry, although its stomach 

 will be then found to still contain much food. It is said to take three days' 

 abstinence to empty the stomach of the domestic rabbit. But here the 

 stomach after abstinence, although distended, is not so distended as before, and 

 the absolute value of the limen of "relaxation stimulus" may legitimately be 

 variously placed. Also, it has been urged that many persons do not feel hungry 

 in the morning after the longest abstinence of the twenty-four hours ;— most 

 English do, but few French or German, a difference related to difference in 

 national habit regarding meal-time. In duodenal fistula hunger has been 

 observed as a marked symptom, even when the stomach is full. On the other 

 hand, in gastric catarrh hunger may be absent although the stomach remain 

 empty for hours. The nature of the stimulus causing the hunger sensations, 

 referred to the epigastrium, is therefore not clear. Tension of the stomach wall 

 (or relaxation) is, however, indicated by various of the above evidences as 

 playing some part in it. Normal tensions, and abnormal, are well known to 

 be efficient as stimuli for the afferent nerves of hollow viscera {e.g. urinary 

 bladder, heart, etc.). The tension caused by the engorgement of the mucosa 

 with the proper digestive granules developed in the cells, may give rise to this 

 local sensation in the case of the stomach. 



As to the sensory nerve channel for the local sensation of hunger, likely 

 enough it is the vagus, but very possibly the stomach receives sensory nerve 

 fibres also from the thoracic spinal ganglia, via the rami communicantes. 

 After section of both vagus nerves, rabbits continue to feed well, and therefore 

 must have appetite. 1 So also, after section of the cervical cord or of both the 

 splanchnic nerves, and after extirpation of the ganglia cceliaca and meseraica. 2 

 Neither the vagus nor the splanchnic afferent channels are therefore necessarily 

 the single channels for the feeling of hunger ; but that after their section the 

 local feeling of hunger exists, is only presumed. Section of merely a few mus- 

 cular nerves would hardly relieve the body from the heavy feeling of fatigue 

 consequent on a long march ; would section of the vagi remove the oppression 

 of impending asphyxia 1 Section of the sensory nerves of the pharynx 

 and oesophagus does not prevent the occurrence of thirst, but moistening 

 the fauces does temporarily allay thirst. 



The dog exhibits hunger after complete removal of the stomach, 3 so 



1 Leuretand Lassaigne, " Rech. physiol. ct chim. p. servira l'histoire de la digestion," 

 Paris, 1825, p. 211 ; Sedillot, "Du nerf pneumog. et ses fonctions," Paris, 1829; Longet, 

 " Physiol, d. systeme nerveux," Paris, 18b'0, tome ii. p. 535 ; Budge, " Lehrbuchd. speciel. 

 Physiol, d. Menschen," Leipzig, 1862, S. 691. These refute Brachet's conclusions, 

 "Recherches s. 1. fonct. d. systeme nerveux," Paris, 1837, p. 219. 



3 Budge, Nova acta phys.-med. Acad. not. curios, 1860, tomo xxvii. 



3 Ludwig and Thanhofer, (quoted from Beaunis, " Les sensations internes," Paris, 1889, 

 p. 34. 



