1918] Bovard: Nervous Impulses in the Earthworm 109 



Discussion. If a worm is etherized by the vial method and allowed 

 to creep on a damp surface, such as moist filter paper, it will be seen 

 to act like a normal worm in every way, except that the middle or 

 etherized portion takes no part in the contractions. "With each pull 

 of the anterior piece it will stretch and passively contract as the pos- 

 terior piece moves up, without showing the normal waves of muscular 

 contraction seen in the active portions. 



A worm, that is moving anteriorly, will reverse its direction and 

 creep posteriorly if stimulated on the anterior end. Stimulation of the 

 posterior end reverses the direction again. This indicates that nerve 

 impulses may pass up or down the nerve cord and that these impulses 

 may change the direction of the creeping movement, but it does not 

 indicate that the impulses responsible for the actual creeping pass 

 through the nerve bridge. There is still the fact that the muscles in 

 the etherized section attaching the anterior to the posterior part may 

 act as the "string" in Friedlander's experiment and give the neces- 

 sary pull which keeps the two parts working in coordination. 



Conclusion. These simple experiments only show that there may 

 be transmission of locomotor impulses in both directions through the 

 nerve cord in an anesthetized region of the worm. 



TENSION 

 (a) Experiments with Etherized Worms 



Problem. To what extent is the factor of tension or pull respon- 

 sible for normal locomotor reactions? 



Method. By the use of ether in anesthesia we are able to test out 

 the importance of the matter of tension or pull in the transmission of 

 locomotor impulses. It will be remembered that the etherized part 

 acts as one piece. No waves of contraction pass up or down this part. 

 A small piece of cork was glued to a glass plate and the glass plate 

 kept wet. A worm prepared by etherizing ten segments in the middle 

 portion was pinned to the cork so that the anterior and posterior parts 

 were free to move, but the middle part was fixed. 



Discussion. Under these conditions no movements of the anterior 

 part could exert any pull on the posterior piece. In all such experi- 

 ments the worms behaved as Biedermann (1904) reported, the pos- 

 terior piece responding with locomotor reactions in perfect coordina- 

 tion to all attempts of the anterior piece to make creeping movements. 

 These movements could not be accomplished because of the slippery 



