992 CUTANEOUS SENSATIONS. 



here is, together with the local excitation, a general condition produced. 

 As to this latter, again, its nature is not clear. A man is usually less hungry- 

 after his ten hours' fast, which has included the night's rest, than after 

 a four hours' abstinence in the working day. The stomach is certainly 

 as emptied in the former case as in the latter. But the greater metabolism 

 that has intervened in the latter brings about a general change which causes 

 hunger. To say this change is want of food-material in the body, is merely to 

 restate the problem. It has been argued that it is want of blood or lymph. 

 Where in duodenal fistula, despite replenishment of the stomach with food, 

 hunger develops and persists, it is relieved speedily by introducing the products 

 of gastric digestion into the upper end of the small bowel. 1 Similarly thirst is, 

 without drinking, rapidly assuaged by tbe injection of fluid into a vein. 2 These 

 effects resemble the production of, and relief from, general muscular fatigue, 

 given by transfusion of blood in Mosso's well-known experiment. 3 The blood 

 is somewhat inspissated in moderate hunger. 4 The relief occurs so rapidly, 

 that it is argued that it may be due to alteration of the blood rather than of 

 the lymph. How quickly large quantities of fluid may be transferred from 

 the blood to the lymph, is shown by experimental observations. 5 The feeling 

 of hunger is relieved, is even converted into a pleasurable satiety, before the 

 blood is saturated with absorbed material. The chief use of the local peripheral 

 reference of sensation in hunger seems as an index for regulating the amount 

 of intake, and thus preventing excess. It has been remarked that animals 

 in which the vagi have been cut, so far from not evincing hunger and taking 

 insufficient food, take an excessive quantity. But I have seen in the dog 

 distinct diminution of appetite ensue on double vagotomy, after cervical 

 spinal transection. 



The peripheral regions to which the feeling is chiefly referred, stomach 

 and throat, are innervated mainly by the ninth and tenth cranial pairs. 

 " Hunger " feeling (and " thirst " feeling) are held, therefore, to originate in 

 impressions elaborated by the bulbar centres receiving the roots of those 

 nerves. These centres are perhaps specially sensitive to those qualities of the 

 circulating blood which depend on intake of food, much as the bulbar centre 

 receiving the lung branches of the vagus is specially sensitive to the respiratory 

 quality of the blood. It can hardly be supposed that in the nerve cells of 

 these centres impulses are actually initiated by conditions of the blood supplied 

 to them. Meynert, it is true, argued that functional hyperemia of the brain 

 is felt as pleasurable and anaemic conditions of the brain as the reverse, the 

 central elements perceiving their own nutritive condition. 6 But the condition 

 of their blood affects the excitability of nerve centres ; it may be supposed to 

 increase the excitability of those into which embouch the afferent nerves of the 

 gullet and the stomach. Some nerve centres are remarkably increased in excit- 

 ability by moderate hunger, just as conversely the knee-jerks are found to be 

 diminished shortly after a heavy meal. The thirst which is caused by some drugs 

 subsides after a time without the taking of liquid into the body ; it has been 

 argued here that the effect is due to temporary increased central activity, due 

 to temporary alteration of the blood. It has been several times remarked that 

 the stomach and intestines of fasting animals exhibit remarkably active 

 peristaltic action. A condition of the general blood or lymph can be easily 

 conceived to not only affect the nerve centres centrally, by affecting the 

 nutrition of their ganglion cells, but also by peripheral changes exciting 



1 Busch, Virchow , s Archiv, Bd. xiv. S. 140. 



2 Dupuytren, " Lemons orales," Paris, 1832. 



3 A. Mosso, Alti d. r. Accad. d. Lincei CI. di sc. fis., mat. e not., Roma, May 1887. 



4 Lloyd- Jones, Journ. Physiol., Cambridge and London, 1891, vol. xii. p. 299. 



5 Sherrington and Copeman, ibid., 1890, vol. xi., "Proc. Physiol. Soc," p. viii., ibid., 

 1893, vol. xiv. 



6 ,; Klinische Vorlesungen iiber Psychiatrie, " Wien, 1890, S. 6. 



