1918] 



Bovard: Nervous Impulses in the Earthworm 



111 



In worms in which the entire dorsal wall, the lateral muscles, and 

 the intestine of the etherized part were dissected away and the nerve 

 cord freed from the ventral muscle by cutting the lateral roots, the 

 coordination continued perfect in function between the anterior and 

 posterior portions. It was observed that such specimens, in creeping, 

 did not move with the middle section tense, as a string connecting the 

 two parts, but that often the posterior part moved along rapidly, 

 causing the middle part to buckle so that under these circumstances 

 no pull could possibly have been exerted on the posterior part. When 

 the anterior part was pinned down, the posterior piece still continued 

 its coordinated movements and "telescoped" anteriorly into other 

 parts. 



Conclusion. Tension or pull, while important in normal creeping 

 movements, may be eliminated and the locomotor stimulus will still 

 pass on down the nerve cord for some distance. 



(&) Autotomy 



In the course of administering the anesthesia to the middle portion 

 of the worms, it sometimes followed that the strong contractions 

 would break the muscular walls of the body, a condition of incomplete 

 autotomy. If the animal was released in time the anterior and pos- 

 terior ends would remain connected by the intestine and the nerve 

 cord (fig. 2). 



arvh posf 



Fig. 2. This shows the nervous bridge as made in an incompletely auto- 

 tomized worm. The break in the musculature occurs between the segments. 

 The intestine (int.), with the dorsal and ventral blood vessels (d.bl.v. and v.bl.v) 

 and a portion of the ventral nerve cord (n.) } may be seen. 



Problem. Is the nervous bridge made by incomplete autotomy 

 between anterior and posterior ends of the worm capable of trans- 

 mitting locomotor impulses in both directions as in the etherized 

 worms ? 



