480 



ANNALS NEW YORK ACADEMY OF SCIENCES 



therefore, tliat tlie omission of impulses from the series is not due to 

 conduction block. The longer intervals in the records must be due to 

 failure of one or more impulses to be initiated. 



100 - 

 90 - 



80 - 



70 - 



<n 



-J 



>60 



K 

 UJ 



K 



?50 



ii. 

 o 



UJ ' 



30 



20 - 



10 - 



- 



J — I I I I l_i. 



> ' ( I l_l I I — I — I — I — I — I — I J. < 



8 10 12 14 16 

 DURATION Of INTERVAL (MS.) 



18 



20 22 24 



FiGURG 20. Diagram representing the same data as in figure 19, but extended to over 500 suc- 

 cessive intervals between impulses. Ordinates are number of intervals having a value in each 0.4 

 millisecond range. Inten-als longer than 24 ms. not shown. 



It is difficult to account for these observations, except on the assump- 

 tion that there is, in this nerve fiber, some rhythmic process, with an 

 average period of 6 milliseconds, that maintains its rhythmic quality in- 

 dependently of the initiation of impulses, once the impulses are started. 



Arvanitaki^' and Hodgkin'^ have presented evidence that an impulse, 

 initiated by electrical stimulation in unmyelinated nerve, develops 

 from a local electrical response which occurs at the site of stimulation. 

 Arvanitaki also showed^^ that this local response, which is elicited by 

 electrical stimulation, may be cyclic in nerAcs deprived of calcium. 

 Using the giant nerve fiber of the squid, wo have studied the develop- 

 ment of this local electrical response in nerves excited solely by the 

 removal of calchnn. We had two objectives: (1) to see if the local 

 response appears before the initiation of the first impulse in a train, 

 and (2) to ascertain whether a rhythmic local response could be pro- 

 duced chemically, and independently of conducted impulses. 



