108 SMELL, TASTE, ALLIED SENSES 



to the common chemical sense as contrasted with our 

 sensations of smell, taste, touch, or pain. The curious 

 feeling that comes from vapors that irritate the eyes, 

 nose, or even the mouth has not the remotest relation 

 to touch, smell, or taste and is only distantly suggestive 

 of pain. Pain, however, is easily separated from the 

 common chemical sense by the use of cocaine, and we 

 are, therefore, entirely justified in concluding that the 

 common chemical sense is a true sense with an indepen- 

 dent set of receptors and a sensation quality entirely its 

 own. In the fishes and amphibians it pervades the whole 

 integument but in the reptiles, birds and mammals it is 

 restricted to the partly exposed mucous membranes of the 

 natural apertures, a restriction that doubtless arose as 

 the vertebrate changed from an aquatic to an air-inhabit- 

 ing form. 



5. BiBLIOGEAPHY 



Braeuning, H. 1904. Zur Kennitnisis der Wirkung chemischer Reize. 

 Arch. ges. Physiol, Bd. 102, pp. 163-184. 



CoGHiLL, G. E. 1914. Correlated Anatomical and Physiological Studies 

 of the Growth of the Nervous System of Amphibia, I. The Afferent 

 System of the trunk of Amblystoma. Jour. Comp. Neurol., vol. 24, 

 pp. 161-233. 1919. II. The Afferent System of the head of Ambly- 

 stoma. Jour. Comp. Neurol., vol. 26, pp. 247-340. 



Cole, L. W. 1910. Enactions of Frogs to Chlorides of Ammonium, Potas- 

 sium, Sodium, and Lithium. Jour. Comp. Neurol. Psychol., vol. 20, 

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Ceoziee, W. J. 1915. Ionic Antagonism in sensory Stimulation. Amer. 

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Cbozeee, W. J. 1916. Regarding' Uie Existence of the " Common Chemical 

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HeREICK, C. J. 1908. On the phylogenetic DiflFerejntiation of the Organs 

 of Smell and Taste. Jour. Comp. Neurol. Psychol., vol. 18, pp. 159-166. 



LoEB, J. 1905. On the Production and Suppression of Muscular Twitdi- 

 ings and Hypersensitiveness of the skin by Electrolytes. Studies in 

 Oeueral Physiology, vol. 2, pp. 748-765. 



