288 



Major W. B. Cannon. 



case of hunger — one explaining thirst as a local sensation, the other explaining 

 it as a general and diffuse sensation. These theories require examination. 



The viewfthat thirst is a sensation of local origin has had few advocates, 

 and the! evidence in its favour is meagre. In 1885 Lepidi-Chioti and 

 Fubini* reported observations on a boy of 17, who, suffering from polyuria, 

 passed from 13 to 15 litres of urine daily. When prevented from drinking 

 for several hours, this youth was tormented by a most distressing thirst, 

 which he referred to the back of the mouth, and at times to the epigastrium. 

 The observers tried the effect of brushing the back of the mouth with a 

 weak solution of cocaine. Scarcely was the application completed before the 

 troublesome sensation wholly ceased, and the patient remained comfortable 

 from 15 to 35 minutes. If, instead of cocaine, water was used to brush over 

 the mucous membranes, thirst was relieved for only two minutes. The 

 temporary abolition of a persistent thirst by use of a local anoesthetio, in a 

 human being who could testify regarding his experience, is suggestive 

 support for the local origin of the sensation. The evidence adduced by 

 Valenti is also suggestive. He cocainised the back of the mouth and the 

 upper oesophagus of dogs which had been deprived of water for several days, 

 and noted that they then refused to drink.f One might suppose that the 

 refusal to take water was due to inhibition of the swallowing reflex by 

 anaesthetisation of the pharyngeal mucosa, as reported by Wassilief.J But 

 Valenti states that his animals are quite capable of swallowing. § 



Though these observations are indicative of a local source of the thirst 

 sensation, they leave unexplained the manner in which the sensation arises. 

 Valenti has put forward the idea that all the afferent nerves of the upper 

 part of the digestive tube are excitable to stimuli of thirst, but that 

 suggestion does not advance our knowledge so long as we are left unen- 

 lightened as to what these stimuli are. A similar criticism may be offered 

 to Luciani's theory that the sensory nerves of the buccal and pharyngeal 

 mucosa are especially sensitive to a diminution of the water-content of the 

 circulating fluid of the body ; indeed, that these nerves are advance 

 sentinels, like the skin nerves for pain, warning the body of daiiger.|| No 

 special features of the nerves of this region, however, are known. No 

 special end-organs are known. The intimation that these nerves are 

 peculiarly related to a general bodily need is pure hypothesis. That they 



* Lepidi-Chioti and Fubini, ' Giorn. d. E. Accad. d. Med.,' Turin, vol. 48, p. 905 (1885). 



+ Valenti, ' Arch. Ital. de Biol.,' vol. 53, p. 94 (1910). 



I Wassilief, ' Ztschr. f. Biol.,' vol. 24, p. 40 (1888). 

 § Valenti, ' Cbl. f. Physiol.,' vol. 20, p. 450 (1906). 



II Luciani, 'Arch, di Fisiol.,' vol. 3, p. 541 (1906). 



