THE RECOVERY OF TRANSMISSIVITY IN PASSIVE IRON 



WIRES AS A MODEL OF RECOVERY PROCESSES IN 



IRRITABLE LIVING SYSTEMS. 



Part I. 



By RALPH S. LILLIE. 



(Frotn the Physiological Laboratory, Clark University, Worcester.) 



(Received for publication, June 20, 1920.) 

 I. INTRODUCTORY. 



A striking feature in the phenomena of activation in passive iron 

 wires immersed in solutions of nitric acid is that in acid above a cer; 

 tain critical concentration the reaction is a temporary one, followed 

 immediately by an automatic return of the metal to the passive 

 state. ^ 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 tend- 

 ency 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 main- 

 tain activity in the living system, constant repetition of stimulation 

 is necessary; and similarly chemical activity in a passive wire im- 

 mersed in a sufficiently strong solution of nitric acid (55 or more vol- 

 umes per cent of HNO3, specific gravity 1.42) is an automatically 

 self-limiting process which can be maintained only by repeated con- 

 tact 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 trans- 

 mitted through more than a short distance. This behavior is highly 



^ For a fuller description of this phenomenon of. Lillie, R. S., Science, 1918, 

 xlviii. 51- 



107 



