SMELL, TASTE, AND CHEMICAL SENSE IN VERTEBRATES. 223 



seen in Table I, for each of the three parts of the body tested, a more concentrated 

 solution of sodium chloride is needed for minimum stimulation than of hydro- 

 chloric acid. Hence the effective element in the stimulation by hydrochloric acid 

 cannot be the chlorine ions, which are about equally numerous in the two sets of 

 solutions dilution for dilution, but must be the hydrogen ions. These have been 

 shown by Richards (1898) and by Kahlenberg (1898) to be responsible also for 

 the sour taste in man. 



TABLE I. 



Reactions of Ammoccetes to Sour, Alkaline, Salty, Bitter, and 



Various Parts of the Fish's Body. 



Reagent. 



H(1n 



HC1 n/20 



HCln/40 



HCln/80 



HCln/640.. . 

 HC1 n/ 1,280. . 



HCln/2,560.. 



NaOHn/10. . 

 NaOHn/100. , 



NaOH n/500 . , 



NaOH n/ 1,000 



NaOH n/2,000 



>JaC12n 



XaCl n 



NaCl n/10... 

 XaCl n/40. . . 

 NaCl n/80 . . . 



Quinine ra/10 



Quinine m/20 



Quinine m/40 



Quinine m/640 



Quinine m/1,280 



Cane sugar 2m 



Part of Body Stimulated 



Mouth. 



Backed away. 

 Swam away. 

 Swam away. 

 Swam away. 

 Swam away. 

 Mouth movements only. 

 No reaction. 



Mid-trunk. 



Tail. 



Swam away 

 Swam away 

 Swam away 

 Swam away 

 No reaction, 



Swam away. 



Swam away. 

 Mouth movements only. 

 Mouth movements only. 



No reaction. 



Swam forward. 

 Moved slightly 

 No reaction. 

 No reaction. 

 No reaction. 

 No reaction. 

 No reaction. 





Swam away, 

 Swam away, 

 Swam away, 

 Swam away, 

 No reaction. 



No reaction. 



Swam away. 

 Swam away. 

 No reaction* 

 No reaction. 

 No reaction. 



Swam away. 

 No reaction. 

 No reaction. 

 No reaction. 

 No reaction. 



Darted forward. 



Swam forward. 



Swam away. 

 No reaction. 



No reaction. 

 No reaction. 

 No reaction. 



Swam away. 

 Swam away. 

 Slight movement 

 No reaction. 

 No reaction. 



Swam away. 

 No reaction. 

 No reaction. 

 No reaction. 

 No reaction. 



- 



No reaction. 



Swam away. 

 Swam away. 



No reaction. 

 No reaction 

 No reaction. 



Swam away. 

 Swam away. 

 No reaction. 

 No reaction. 

 No reaction. 



No reaction. 



In a second series of tests on Ammoccetes in which a solution of nitric acid 

 was used in place of hydrochloric acid, results indistinguishable from those in 

 which hydrochloric acid was used were obtained. This is what was to be ex- 

 pected considering the close agreement in the chemical relations of these two acids. 



An alkaline stimulus, a solution of sodic hydrate, was most effective 

 Table I shows, at the mouth, somewhat less so on the tail, and least so on the 

 mid-trunk. By comparing the reactions to sodic hydrate with those to sodic 

 chloride, it can be shown by an argument analogous to that used for the acid 

 reactions, that in the responses to sodic hydrate, the hydroxyl ions and not the 

 sodium ions, are the cause of the stimulation. Essentially similar results to 

 those obtained from sodic hydrate were produced by potassic hydrate 



* 



For a salty stimulus a solution of sodic chloride was used ; this was least stimu 



