1918J Bovard: Giant Fibers in Earthworms 143 



EFFECT OF DRUGS 



If small quantities of cocaine or stovaine are injected into the 

 body cavity of the worm the drugs act as a block on the nerve and 

 affect the transmission through the nerve cord. Cocaine has a more 

 general effect on the worm and produces in many cases very irregular 

 behavior, but stovaine gives very consistent results. The first effect 

 was the loss of giant fiber action through the region. Transmission 

 was perfect above and below the point of injection. As the effect of 

 the drug worked deeper into the cord the transmission of locomotor 

 impulses became more irregular and in some cases was lost altogether. 

 As recovery took place the return of activity was just the reverse. 

 The locomotor impulses became more and more regular until perfect 

 co-ordination was set up. Then the giant fiber action began to show 

 transmissions. Here, too, the same phenomena were seen as in the 

 case of regeneration. Just before giant fiber impulses showed normal, 

 end to end responses, the stimulation of the anterior end showed the 

 characteristic relaxation of the circular muscles in the posterior tip. 

 Very soon after this the end to end movements occur in response to 

 stimuli. 



A record is given below of an experiment with stovaine, which 

 shows the course of events and the relation between giant fiber and 

 locomotor fibers. 



Experiment 188 — Effect of Stovaine on Transmission 

 May 18, 1915, 4:45 p.m. — The worm (Helodrilus caliginosa), douhlj pinned to a 

 cork plate on a glass, was injected with a small quantity of stovaine in 

 the body cavity of the middle region. 



Almost immediately giant fiber action is lost and locomotor trans- 

 mission not normal. 

 5:00 p.m. — Locomotor impulses pass through block, but do not run full length 

 of posterior part. 



Locomotor co-ordination between anterior and posterior parts. 

 As time goes on locomotor movements run further down the posterior 

 part. 

 5:10 p.m. — Any stimulus to the anterior end results in locomotor movements 

 in posterior end. Wave contractions run to posterior tip more frequently. 

 No giant fiber action. 

 5:35 p.m. — Stimulation of anterior end gives increased activity of posterior 

 end. No giant fiber action. Animal apparently normal except no end to 

 end contractions. 

 5:48 p.m. — Giant fiber action returned. Animal fully recovered. 



