. BIOELECTRIC PHENOMENA 307 



corresponds a linear series of potentials, the relation 

 characteristic of electrode-potentials in general. 'J'hat 

 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 Bcutner compared the 

 effects of varying the concentration of the s()luti(Mi in 

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

 (B) a surface from w^hich 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/iooo NaCl +0.146 +0.036 



m/ioo NaCl +0.086 +00.0 



m/io NaCl +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 0.03 volt. With 

 every solution used the altered surface exliibits 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. 



