L. H. HYMAN AND A. W. BELLAMY. 



(galv.) and the negativity diminishing along the antero-posterior 

 axis. 



4. In the oligochsetes the susceptibility gradient was found to be 

 of a characteristic kind (Hyman, '16; Hyman and Galigher, '21). 

 Both anterior and posterior ends are the most susceptible and the 

 susceptibility decreases from both ends toward the middle. It is 

 a very suggestive fact that the electrical gradient in oligochaetes is 

 in agreement with this susceptibility gradient. As first shown by 

 Morgan and Dimon ('04), the anterior and posterior ends of the 

 earthworm are electronegative (galv.) to the middle. This re- 

 markable agreement between the electrical and susceptibility gradi- 

 ents indicates strongly that they have a common physiological basis. 



From a consideration of the facts mentioned above the senior 

 author was led to believe that the bioelectric currents are due to 

 the same factors which are responsible for the susceptibility differ- 

 ences. The susceptibility differences are known to be correlated 

 with metabolic differences. Organisms or parts of organisms 

 which are highly susceptible to toxic agents have a higher metabolic 

 rate than those which are less susceptible. Susceptibility is in- 

 creased by factors which are known to increase metabolic rate 

 and decreased by those which lower metabolic rate. 



It thus appears that the bioelectric currents are correlated with 

 differences in the rate of chemical activity at different levels or in 

 different parts of an organism or tissue, probably chiefly with 

 differences in the rate of oxidation. In general, any region of 

 increased chemical activity becomes ipso facto electronegative 

 (galv.) to any region of lower chemical activity. Injury increases 

 the rate of chemical change (cf. Tashiro, '17) and the injured area 

 develops an electronegativity (galv.). Activity of muscle, nerve, 

 gland, etc., is generally accompanied by an increased rate of 

 respiratory exchange ; hence is also characterized by the appear- 

 ance of an electronegativity. When the differences in rate of 

 chemical change are temporary, the accompanying bioelectric cur- 

 rents are also temporary, as in the case of the current of action; 

 when the differences are permanent, the bioelectric current is like- 

 wise permanent, as in the case of the electrical gradient which 

 exists along the axes of organisms. 



While it appears probable that differences in the rate of oxida- 



