September 12, 1919] 



SCIENCE 



259 



It is recommended that the stations be so located, 

 if possible that the greater part of the work of 

 securing and measuring the films may be done by 

 local scientists. On the other hand, it is recom- 

 mended that the installation of the apparatus be 

 supervised by those who have devised it and had 

 experience with it. It is recommended that all 

 the details of securing the records, measuring the 

 films, and making the calculations be entirely 

 homogeneous and under the supervision of those 

 who have already perfected them. 



Committee of the American Section of the In- 

 ternational Geophysical Union on Earth Tides, 

 A. A. MiCHELSON, Chairman, 



F. R. MOULTON, 



T. C. Chamberlin 



SPECIAL ARTICLES 



RESEMBLANCES BETWEEN THE PROPERTIES 



OF SURFACE-FILMS IN PASSIVE METALS 



AND IN PROTOPLASM. I 



In my recent comparison of protoplasmic 

 transmission with the transmission of activa- 

 tion in passive metals.^ I reviewed evidence 

 indicating that in both eases the effect is de- 

 pendent upon the properties of the thin film 

 of impermeable or protective material formed 

 or deposited at the interface between the 

 metal, or the protoplasm, and the adjoining 

 electrolyte solution. In the passive metal the 

 comjKJsition and physical properties of this 

 thin layer are such that it is very readily and 

 rapidly altered or removed by the electro- 

 chemical action of the local circuits which ap- 

 pear wherever the film is locally interrupted 

 or its permeability increased beyond a certain 

 limit. The originally continuous and homo- 

 geneous film (of oxide or oxygen compound) 

 may thus be removed by electrolytic reduction 

 at the local cathode; a new local circuit is 

 then automatically formed at the boundary 

 between this reduced or activated region 

 (where metallic iron is exposed) and the film- 

 covered or passive area beyond, which forms 

 the cathode of the circuit; a similar process 

 is there repeated; and in this manner the 

 active state is propagated over the whole sur- 



1 Science, N. S., 1918, Vol. 48, p. 51; cf. also 

 my general article on "Protoplasmic Transmis- 

 sion," Scientific Monthly, 1919, Vol. 8, pp. 456, 

 552. 



face of the metal. Similarly in the living 

 system, e. g., nen^e-axone (according to the 

 local action theory of protoplasmic transmis- 

 sion), the surface-film or plasma-membrane is 

 locally altered or interrupted in an analogous 

 manner by the action of the local bioelectric 

 circuit formed between the region of excita- 

 tion and the resting region beyond; at this 

 latter region, where the current (positive 

 stream) of the circuit passes from the proto- 

 plasmic surface to the medium, it produces, 

 primarily through some local process of elec- 

 trolysis, a change — the critical or excitatory 

 change — in the structure and electromotor 

 properties of the surface-film, this change 

 being apparently associated with an interrup- 

 tion of continuity or increased permeability; 

 a new circuit then arises at the boundary 

 between this newly altered or activated area 

 and the adjacent still unaltered area; and by 

 a repetition of this process at each new active- 

 resting boundary as it is formed, a wave of 

 chemical and physical alteration, associated 

 with a local electrical circuit, travels over the 

 surface of the irritable element. This wave 

 constitutes the excitation-wave, or nerve im- 

 pulse in the case of the nerve-axone. Since 

 by its very nature this wave is always asso- 

 ciated with a local electric current, it produces 

 the effects of electrical stimulation wherever 

 it extends, hence also in the irritable structure, 

 e. g., muscle-cell, at which the axone term- 

 inates. 



This theory postulates an essential similar- 

 ity in physicochemical properties and consti- 

 tution between the surface-films of passive 

 metals and the protoplasmic surface-films or 

 plasma-membranes of the irritable living cells 

 or cell-structures. Certain general resem- 

 blances are apparent: both types of film are 

 water-insoluble, are formed by chemical alter- 

 ation (typically involving oxidation) of the 

 surface-layer of the metal or protoplasm, are 

 impermeable or difficultly permeable to the 

 electrolytes of the adjoining solution, and are 

 subject to ready alteration under the influence 

 of electric currents formed by local action. 

 In consequence of this latter condition such 

 films are often unstable and subject to com- 



