PRECIPITATION STRUCTURES SIMULATING ORGANIC GROWTH. 245 



ruption of the surface-film is thus at once automatically repaired, 

 since that region, by the exposure of the underlying metal, is 

 rendered anodal, and hence becomes the site of formation and 

 deposition of the passivating surface-film. Similarly in the 

 production of the local bioelectric circuit, e. g., in a stimulated 

 nerve, there is apparently a physical and chemical alteration of 

 the protoplasmic surface-film, involving increased permeability, 

 at one region, that of excitation; this altered region becomes 

 electrically negative, so that the positive stream of the resulting 

 bioelectric current there re-enters the protoplasmic surface; and 

 apparently it there effects an oxidative synthesis which restores 

 the resting condition. According to this conception, construc- 

 tive or "anabolic" processes predominate at the regions where 

 the current enters the protoplasm from outside; while at the 

 adjoining inactive regions where the current leaves, and where a 

 new state of excitation is automatically aroused, it is to be as- 

 sumed that processes of the reverse kind take place. 1 



It is interesting to note that many years ago, before the de- 

 velopment of modern physical chemistry, Hering reached very 

 similar conceptions of the relation of the electric current to 

 stimulation and to vital activity in general. 2 He rejects Du 

 Bois-Reymond's purely physical conception of the origin and 

 significance of the bioelectric currents, and recognizes that they 

 are essentially indexes of chemical cha'nges in the living matter. 

 Similarly, external electric currents affect living matter primarily 

 through their chemical or metabolic influence; where the current 

 enters the protoplasm assimilatory (anabolic) processes predomi- 

 nate, and where it leaves, dissimilatory (catabolic) ; the stimu- 

 lating and electrotonic influences of the current are referred to 

 these characteristic influences on metabolism. These concep- 



1 Since such constructive processes are the condition of growth, we should 

 expect, according to this hypothesis, that the constant electric current in influ- 

 encing growth should promote the latter where the positive stream enters the 

 tissue (i.e., at the anode of the pair of applied electrodes) and inhibit where it 

 leaves (at cathode). According to the recent observations of Bose (Proc. Roy. 

 Soc., B, Vol. 9, p. 364) this is the case in plant growth. " In the polar action of 

 electric current 01 growth, ths atiDi? is found to enhance and the cathode to 

 depress the normal rate " (p. 399)- 



2 Hering, "Theory of the Functions in Living Matter," Brain, 1897, Vol. 20, 

 p. 232 (translation of article in Lotos, IX., Prag, 1888). 



