BIOELECTRIC PHENOMENA 307 



corresponds a linear series of potentials, the relation 

 characteristic of electrode-potentials in general. That 

 the effect observed in any single case depends on the 

 special character of the surface was shown in a series of 

 experiments in which Loeb and Beutner compared the 

 effects of varying the concentration of the solution in 

 contact with (A) the uninjured surface of an apple, and 

 (B) a surface from which the skin had been removed/ 

 In all such experiments one electrode in contact with 

 the apple remained unchanged; the other was connected 

 with the solution which was varied; the latter was in 

 contact with another portion of the surface at some 

 distance from the first electrode. A quadrant electrome- 

 ter was used. 



Potential Difference Observed with Solution in Contact 



Solution A (with uninjured skin) B (with cut surface) 



m/io,ooo NaCl +0.175 +0.056 



m/ioooNaCi +0.146 +0.036 



m/iooNaCl +0.086 +000 



m/ioNaCl +0.023 -0.022 



Both surfaces show the same kind of variation with 

 varying concentration of electrolyte, but the altered area 

 shows a smaller change of potential for a given change of 

 concentration; thus on the average a tenfold dilution 

 increases the positivity of the unaltered surface by about 

 0.06 volt, and of the altered by about^o.03 volt. With 

 every solution used the altered surface exhibits the lower 

 potential; i.e., is negative relatively to the unaltered; 

 the conditions also suggest that it represents an area 

 which is reversible to anions as well as to cations,^ 



^ Loc. cit., 1912. 



2 This would correspond to freer penetration by anions and an 

 entrance of diffusion potentials in the total effect. 



