CORRELATION BETWEEN METABOLIC GRADIENTS. 32! 



Recently R. S. Lillie ('17, '19, '22, and others) in a number of 

 interesting and suggestive papers has been inclined to attribute the 

 origin of potential differences in organisms, particularly of the 

 current of action, to local chemical change, which concerns chiefly 

 the limiting membrane. This conception is added to Lillie's for- 

 mer views of the role of depolarization of the surface membrane 

 in the causation of the current of action. Thus Lillie says ('22, 

 p. 17) : "Apparently any rapid local decrease of surface polariza- 

 tion (sufficient in range) causes stimulation in the typical irritable 

 system such as muscle and nerve. This purely physical change, 

 however, is merely the precursor or determinant of the local stimu- 

 lation reaction ; it is not the reaction itself. The latter is a physi- 

 ological process dependent, like all such processes, on chemical 

 reactions." Lillie is also further of the opinion that bioelectric 

 circuits may be oxidation-reduction circuits. 



The conception set forth in this paper, that potential differences 

 in organisms originate in differences in metabolic rate, has been 

 mentioned briefly in several publications from this laboratory- 

 c.g., Child, '15, pp. 63-64, and '210,, pp. 44-46. The senior author 

 has also published a preliminary general paper (Hyman, '18) in 

 which her views are more fully set forth than in the present paper 

 and to which the reader is referred for further details. 



The preceding pages attempt to give some account of the de- 

 velopment of one idea concerning the origin of the bioelectric 

 currents. The consideration of other suggestions concerning these 

 currents involves the working over of a large literature and is 

 deferred for the present. It may, however, be stated that there 

 are two other principal suggestions as to the causation of these 

 currents. One of them may be referred to as the concentration- 



j 



cell theory and the other as the membrane-depolarization theory. 

 These two ideas are more or less intermingled and most investi- 

 gators who have supported the concentration-cell theory have 

 postulated membranes to bring about the concentration differences. 

 The idea that the bioelectric currents arise from concentration 

 chains has been ably discussed by Bernstein, '02, '12; also by 

 Cremer ('06), where earlier references will be found. Bern- 

 stein's analysis shows that there are three types of chemical chains 

 setting free electricity : those in which the electric energy decreases 



