250 PROTOPLASMIC ACTION AND NERVOUS ACTION 



the whole mercury surface is film-covered and inactive 

 and is flattening as a result of the lowering of surface- 

 tension, a rupture of the film appears, usually at the 

 margin of the drop, disclosing the bright metalHc surface 

 beneath. Instantly an effervescence starts at the edges 

 of this fissure and then sweeps over the whole surface of 

 the metal; a new film is then formed and the cycle is 

 repeated. In an inactive drop, an artificial mechanical 

 rupture will often initiate a reaction which similarly 

 spreads rapidly over the whole surface. 



Bredig found that a stationary film formed over an 

 inactive surface of mercury is quickly dissolved by render- 

 ing the metal cathode;^ in this process of dissolution 

 oxygen is freed. The essential condition of the transmis- 

 sion thus becomes clear. When a film-covered and a 

 bright area of the mercury surface adjoin each other, 

 e.g., after a local rupture of the film, a local electrical 

 circuit is formed between the two, the film-covered 

 area being the cathode of the local circuit. The current 

 of this circuit has the effect of dissolving the film, by 

 cathodic reduction, for a certain distance (estimated at 

 1-3 millimeters) from the boundary, oxygen being freed 

 in the process; and by repetition of this effect at each 

 new boundary as soon as it is formed the effect spreads 

 rapidly over the whole surface. The Hg-HaOa pulsating 

 catalysis thus in reality represents an intermittent 

 electrolysis of H2O2 under the influence of the temporary 

 local circuits formed during the alteration or removal 

 of the surface-film. 



Rhythmical chemical processes at the surfaces of 

 metals immersed in electrolyte solutions containing 



^ Cf. Bredig and Wilke, op. cit., p. 69. 



