Fresh water applied to the frog's tongue produces a massive volley of large fibre impulses in the gloss pharyngeal nerve lasting for some minutes. (The observations were made upon winter frogs.) This water response of the large fibre endings is abolished by Ringer solution, NaCl and some other salts in isotonic solutions but not by isotonic cane sugar solution. KCl exerts a general inhibitory effect upon the large fibre endings of the tongue, while CaCl2 does not only fail in abolishing the water effect but excites also the small fibre endings of the tongue. Quinine sulphate, 0.3 % in Ringer, stimulates highly the endings of the small fibres and produces a long lasting paralysis of the large fibre endings. The physiological significance of the water effect upon the frog's tongue is briefly discussed. It is suggested that it takes part in the regulatory mechanisms of the ionic balance.
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Yngve Zotterman (1949) studied this question.