1918] 



Bovard: Nervous Impulses in the Earthworm 



121 



Mt 



vvAAAAAAAAAA/Wv^v-A^ — -c 



A := Short piece of whole worm with nerve cord. 

 B = Dorsal longitudinal half without nerve cord. 

 C ^ Ventral longitudinal half with nerve cord. 



Fig. 10. Experiment 104. Curve A is made by a short piece of worm 

 attached to a writing lever. The piece was normal in every way and gave 

 rhythmical contractions. Curve B rejiresents a curve made by the dorsal half 

 of a short piece of a worm that had been split in two longitudinally. This 

 piece contained no nerve cord. Curve C was made by the ventral half of a 

 short piece of a worm that had been split in two longitudinally. This piece 

 did contain the ventral nerve cord and did give rhythmic contractions. 



My results agree entirely with those of Budington. It is quite 

 possible that the findings of Straub may be due to a factor that he 

 overlooked, the matter of regeneration. As I shall show in a later 

 paper, regeneration is exceedingly rapid and there is a possibility that 

 nerves have grown into the operated portion, and the probability is 

 that Straub was really dealing with pieces in which nerve fibers and 

 cells had regenerated. 



As further evidence of this dependence upon the nerve cord for 

 transmission it will be noted that when a worm is pinned in the middle 

 portion to a cork plate and the anterior and posterior ends are regis- 

 tering coordinated movements on a revolving drum, if the nerve be 

 cut in the pinned region the rates of contraction of the two parts will 

 be immediately changed. In this case, the muscle is disturbed as little 

 as possible and only the nerve cord is cut (fig. 11). 



Read in this direction 



Fig. 11. Shows how the posterior half of the worm changed its rhythm after 

 the nerve cord had been cut. The upper line represents the movements of the 

 anterior (A) half and the lower line the posterior (B) half. The nerve cord 

 was cut without cutting any but a small portion of the ventral muscle. 



Conclusion. — From the work just cited, it is quite certain that 

 spontaneous movements are dependent on the nervous tissue and that 



