RALPH S. LILLIE 117 



The rate of recovery, as measured by the gain per unit of time in 

 the traveling power of the wave, is at first gradual and then more 

 rapid. Transmission for the full distance of 20 cm. is equivalent to 

 transmission for an indefinite distance ; it is in fact unusual for a wave 

 that has traveled 16 cm. (at 20°) to fail to travel the whole length of 

 any wire. Transmission for 20 cm. thus signifies full or complete 

 transmissivity. If we define transmissivity in numerical terms as 

 the distance in centimeters which the wave is capable of traveling 

 along a homogeneous wire before spontaneous extinction, its values 

 range from unity or less to infinity, the latter value signifying trans- 

 mission without progressive decline in traveling power. This condi- 

 tion corresponds to an ''all or none" behavior, or conduction without 

 decrement, in a living conducting tissue like nerve; partial transmis- 

 sion is equivalent to conduction with a decrement; the numerical 

 measure of this decrement may be defined as the reciprocal of the 

 distance traveled before extinction. 



The behavior of different wires under otherwise identical conditions 

 is subject to considerable variation, due apparently to accidental dif- 

 ferences in the structure of the metal in the different wires. Thus 

 there are occasional exceptions to the rule of an increase in the dis- 

 tance of transmission on passing from one member of a series to the 

 next. Table I gives the results of seventeen separate series of deter- 

 minations with wires immersed in 65 volumes per cent of 1 .42 acid 

 ( = about 9 N by volume) . These series were all carried out on a single 

 day, using two sets of ten wires each; these were used alternately, a 

 determination with the one set being made while the other was under- 

 going repassivation in strong acid. There are thus eight series of 

 observations with the one group and nine with the other; the wires 

 were placed in random order in each series; i.e.^ no care was taken to 

 treat each wire individually as in the experiments to be described later. 

 The figures give the distances in centimeters traveled by the activa- 

 tion wave along the wire when the latter is touched at one end with 

 zinc after the intervals (since the previous complete activation) given 

 at the head of the column. Each horizontal line gives the observa- 

 tions with a single series. The temperature of the acid was constant 

 between 20 and 21°. 



