248 PROTOPLASMIC ACTION AND NERVOUS ACTION 



that many vital processes (stimulation, cell-division) 

 are also dependent on changes undergone by surface- 

 films — those forming the plasma membranes and other 

 protoplasmic partitions — this feature of the H2O2 ca- 

 talysis suggests that the foregoing physiological parallel 

 may be more than a superficial one, and that the similari- 

 ties depend on a fundamental identity in the conditions 

 controlling the course of the reactions in the two systems. 

 It is necessary therefore to examine more closely into 

 the nature of the conditions controlHng the activity of 

 the Hg-HaOa system. 



The rhythm is best shown in 10 per cent aqueous 

 solutions of H2O2. The film which forms over the surface 

 of pure mercury in this solution is gold-brown in color, 

 and the conditions for the rhythmical reaction are best 

 when the solution is shghtly on the alkaline side of 

 neutrality. The evolution of oxygen occurs during the 

 breaking down of the film; when the film covers the 

 entire surface of the mercury the reaction ceases. If 

 the solution is shghtly acid, the film is stabilized and 

 no evolution of gas occurs; at the appropriate degree of 

 alkahnity it is alternately formed and broken down with 

 a regular rhythm of about ten to fifteen per minute 

 (at 18°) . The film shows great sensitivity to the presence 

 of foreign substances, including salts and surface-active 

 organic compounds (such as ether and olive oil); the 

 latter abolish the rhythm.^ It is also highly susceptible 

 ,to changes in electrical polarization. Many other 

 striking parallels with physiological rhythms are 

 described in the article by Bredig and Wilke.^ 



^ Cf. Bredig and Weinmayr, Z. physik. Chem., XIJI (1903), 601. 

 ' Biochem. Zeitschrift, XI (1908), 67. 



