140 



University of Calif orma Publications in Zoology [Vol. 18 



The following table, no. 182, shows a series of worms and regen- 

 eration of nerve cord as expressed by the return of physiological 

 activity. 



Experiment 182 — Eegeneration of Nerve Cord After a Simple Transvese 



Section 



Time in days when impulses are again possible in Transmission Fibers and Giant Fibers 



A P — transmission from anterior end to posterfor end. 

 P A r= transmission from posterior end to anterior end. 



Stimulation of the anterior end causes the end to end jerk of 

 muscles as far as the cut, but behind this no such movement arises. 

 With each stimulus there will be seen, in the posterior tip, a relaxation 

 of the circular muscles and a dorso-ventral flattening. The chaetae 

 will be projected and directed forwards, but there is no movement of 

 the longitudinal muscles. A few hours later the ^ame movement will 

 be accompanied by a distinct jerk of the longitudinal muscle, and the 

 next day a well co-ordinated, end to end contraction will be added to 

 the reaction. 



Removal of Sections of the Cord 



When small sections of the cord were removed, as shown in the 

 following table, the return of physiological activity was in the same 

 order as when simple transverse sections were made. The time for 

 regeneration and complete recovery was lengthened, but was still sur- 

 prisingly short. 



