THE RECOVERY OF TRANSMISSIVITY IN PASSIVE IRON WIRES AS A MODEL OF RECOVERY PROCESSES IN IRRITABLE LIVING SYSTEMS. PARr I. BY RALPH

A striking feature in the phenomena of activation in passive iron wires immersed in solutions of nitric acid is that in acid above acer tain critical concentration the reaction is a temporary one, followed immediately by an automatic return of the metal to the passive state. 1 Activation initiated at any region of such a wire is thus trans~ mitted rapidly along its whole length in a wave-like manner, each region as it becomes active activating the region next adjoining (by means of the local electric circuit between the passive and active areas) and immediately becoming itself again passive. In this tendency to revert promptly to the chemically inactive or passive state after activation the passive metal resembles an irritable and conducting living element such as a nerve fiber or muscle cell. In order to maintain activity in the living system, constant repetition of stimulation is necessary; and similarly chemical activity in a passive wire immersed in a sufficiently strong solution of nitric acid (55 or more volumes per cent of HNO3, specific gravity 1.42) is an automatically self-limiting process which can be maintained only by repeated contact of the activating metal; e.g., zinc. Even under such conditions only a partial and irregular activity is possible, which is confined to the immediate neighborhood of the contact; i.e., it fails to be transmitted through more than a short distance. This behavior is highly