STRUCTURES RESEMBLING ORGANIC GROWTHS. l8l 



on becoming positive may then combine with the negative ions 

 present which may be oxygen or hydroxyl or other available 

 anions, according to concentrations, affinities, etc. and the 

 material assumes a higher state of oxidation; other transforma- 

 tions, including syntheses, may follow from this change. Such 

 a process implies that a positive electrical stream enters the 

 cell-surface from the medium at the site of oxidation, and leaves 

 the cell at other regions; at the latter regions presumably cations 

 are given off from the cell-surface (which appears to act as a 

 reversible electrode relatively to cations). A circuit thus flows 

 through cell and medium, the positive stream flowing in the 

 external medium toward the region of oxidation and away from 

 the resting or chemically inactive regions. In other words, the 

 local combination of oxygen with the cell-surface at any regioa 

 involves the entrance of positive charges at that region, in a 

 manner analogous to the entrance of positive charges at the 

 cathode in the oxygen-hydrogen cell. So far as the physio- 

 logical evidence extends, the region of highest oxidation-rate in 

 cells does appear always to be negative (in the physiological 

 sense) toward regions of lower oxidation-rate. This is indicated 

 by the general fact that stimulated or active regions are negative 

 relatively to inactive regions, oxygen being typically required 

 for such activity; actively growing regions appear also to be 

 negative relatively to less active or non-growing regions; this 

 is seen in the regeneration of hydroid stems and of the tails of 

 fishes, and in the growth of seedlings, 1 and is probably general, 

 although at present the observations are insufficient to establish 

 this generalization empirically. In such cases the negative 

 regions i. e., the regions where the positive stream enters the 

 cells from outside are the regions of most active constructive 

 metabolism; and since oxygen is required for growth and re- 

 generation, this fact may be regarded as an expression of the 

 general connection between oxidation-processes and syntheses. 

 It should be added that changes in the local physical or chemical 



1 Cf. Mathews, loc. cit. For the case of seedlings cf. Miiller-Hettlingen, Pfliiger's 

 Archlv, 1883, Vol. 31, p. 193. Hermann first observed that the growing root-tip 

 in seedlings was strongly negative to other regions (Pfliiger's Archiv, 1882, Vol. 27, 

 p. 288), and Miiller-Hettlingen followed the subject further at Hermann's sug- 

 gestion. 



