Resemblances between the Electromotor Varia- Tions of Rhythmically Reacting Living and Non-living Systems by Ralph

I t is well known that under certain conditions the reaction of iron wire with nitric acid exhibits an automatic r h y t h m of sometimes remarkable regularity, consisting in an alternation of active and passive periods. 1 In a recent study of this phenomenon ~ I have found the most regular rhythms in soft iron wire of low carbon content. Wire drawn from iron prepared by electrolysis of pure solutions of iron salts 3 and the pure commercial soft iron known as ArmcO are especially favorable. In hard steel wire (piano wire) the tendency to rhythm is slight, and any rhythm shown is local and irregular. In general the essential conditions for a regular and rapid rhythm (e.g., 50 to 100 per minute), involving all parts of a wire of some length (10 cm. and more), may be defined as follows: (1) The acid must be of sufficient strength (>55 v.%), such that the passive state is one of stable equilibrium; the wire then reverts automatically to the passive state after each activation (spontaneous repassivation); (2) the wire must transmit states of activation readily and quickly; (3) it must recover its transmissivity rapidly after activation; and (4)