1918] Bovard: Nervous Impulses in the Earthworm 105 



view, then, the nerve cord is supplementary and concerned only with 

 those short reflex paths which are mediated by a single ganglion. 

 Previous to the year in which Friedlander published his analysis of 

 the movements of earthworms, Krukenberg (1881) showed, in some 

 work on leeches, that the middle section of the animal could be 

 anesthetized with the result that the parts anterior and posterior to 

 this region still acted in perfect coordination. In these animals, how- 

 ever, the nervous system differs structurally from that of an oligo- 

 chaete. In leeches the nerves run from the anterior to the posterior end, 

 while in the oligochaetes the only long nerves are the giant fibers, the 

 other fibers in the cord being those of short neurones extending at 

 most from one ganglion to the next. The anesthesia in leeches affects 

 only the peripheral nerve endings, while the trunks connecting anterior 

 and posterior portions are not affected. 



The more recent work of Biedermann (1904) becomes particularly 

 interesting, however, as it gives some new light on the function of the 

 nerve cord of the earthworm. In this work on the comparative physi- 

 ology of peristaltic movements he compares the locomotor action in 

 earthworms to the rhythmic movements found in smooth muscle. 

 Biedermann discovered that if worms were placed in seven per cent 

 alcohol for a few minutes until they became motionless and then the 

 middle region of several segments was anesthetized with nitric acid or 

 pure chloroform for a few seconds, the muscular activity of the sec- 

 tion was destroyed and all response to stimulus failed. He then had a 

 worm with active anterior and posterior parts connected through the 

 anesthetized area by a nerve cord. In creeping movements, the 

 anesthetized area, or dead area, acted as one piece. It transmitted 

 no rhythmic movements, while the posterior part still acted in perfect 

 coordination with the anterior part. 



In further tests by Biedermann of the transmission of impulses 

 through the cord over more than one segment, he pinned such anes- 

 thetized specimens to a cork plate by needles through the dead mus- 

 cular area and found that the posterior part still moved in perfect 

 coordination with the anterior part. With regard to the limits of this 

 transmission through the cord, and the speed of the impulses, it is 

 stated in his paper (1904, p. 493) that the transmission often runs 

 2-3 centimeters in 4-5 seconds. 



In the interpretation of these experiments Biedermann accepts the 

 theory proposed by Friedlander, except that in order to explain the 

 coordinated movements of posterior pieces when a certain part was 



