.RALPH S. LILLIE 143 



transmissivity. The former phase is of brief duration and is indicated 

 by a sudden change in the electrical potential of the wire, from that 

 of active to that of passive iron ; this phase is succeeded by the second 

 and more prolonged period during which the passivating layer under- 

 goes the progressive alteration associated with the recovery of trans- 

 missivity. This alteration appears to consist in a progressive thinning 

 of the passivating film until a minimal thickness of (probably 1 m.ole- 

 cule) is attained. Further thinning is prevented by local electro- 

 chemical oxidation. 



6. The phenomena of partial or limited transmission during the 

 second phase of the recovery process show a close correspondence 

 with the phenomena of conduction with decrement in irritable living 

 tissues such as nerve. Other analogies with the behavior of irritable 

 tissues (threshold phenomena, distinction between "local" and "prop- 

 agated" effects, summation, effects resembling electrotonus) are 

 described. 



