PRECIPITATION STRUCTURES SIMULATING ORGANIC GROWTH. 243 



other regions. The evidence now available indicates that this 

 condition is a general one, and that in growing tissues and or- 

 ganisms (both animals and plants) the regions of preponderant 

 growth are typically electronegative (in the physiological sense) 

 to less actively growing regions, i. e., at the actively growing 

 regions the positive stream of the bioelectric circuit enters the 

 living cells from the surroundings. It is well known that in 

 irritable tissues the physiologically active or stimulated regions 

 are negative to resting regions; growth appears to agree with other 

 forms of functional activity in the character of its bioelectric 

 manifestation. The fact that functional activity is in general a 

 condition favorable to growth is probably to be connected with 

 this fundamental similarity, and suggests -that the bioelectric 

 currents associated with activity have themselves a growth- 

 furthering influence upon the tissue. Now organic growth 

 implies the synthesis of specific compounds, especially of pro- 

 teins; apparently therefore this synthesis is favored where the 

 positive stream enters the protoplasmic surface from the outside. 

 In the typical irritable tissue like muscle or nerve the bioelectric 

 current leaves the irritable element at the resting regions and 

 enters it at the active region ; but activity at the latter region is 

 usually temporary, unless stimulation is continued, and it is 

 probable that the normal automatic return to the resting state is 

 directly determined by the re-entrance of the current into the 

 irritable element at the active area. 1 We know that a positive 

 electrode from an external source of current has an inhibiting 

 effect when applied to an active area of tissue, and the same effect 

 must result at the entrance-region of the current generated by 

 the tissue in its own activity. 



All of these facts receive a consistent unitary interpretation 

 on the hypothesis that the entrance of the electric current (posi- 

 tive stream) into the protoplasm induces or promotes certain 

 oxidation-processes, primarily in the surface-film, and that these 

 oxidations form a necessary condition of the synthetic processes 

 by which the specific structural material of protoplasm is built 

 up. In the actively growing cell or organism this synthesis 



1 The automatic repassivation of iron in strong HNOs offers a close physico- 

 chemical analogy; cf.. my paper in Science, loc. cit., p. 55. 



