1918] Bovard: Nervous Impulses in the Earthworm 107 



cotton soaked with ether, was then turned down over the worm so that 

 the mouth of the bottle covered the middle section of the worm. It 

 was possible to hold this in place over the squirming worm until the 

 middle part was anesthetized. Owing to the slipperiness of the plate, 

 the worm could get no hold and autotomy was very rare. When, 

 however, as occurred in early experiments, this method was tried on a 

 cork plate, autotomy of the anterior or posterior part was frequent 

 because of the hold the chaetae were able to take on the cork and so 

 the worm could pull itself in two. Exposure of two minutes to ether 

 fumes was sufficient for complete anesthesia, but had little effect on 

 the muscle tissue itself. The worms usually recovered completely from 

 the effects of the treatment in from ten minutes to an hour. During 

 this time a stimulus to the muscle in the anesthetized area called forth 

 a direct response but started no reactions in the untreated parts of 

 the worm. 



In using some of the larger worms this simple method was varied 

 by treating the etherized area with six per cent nitric acid for ten 

 seconds, then washing the whole worm in water; this made certain 

 that the sensory nerve endings, of this part, were rendered functionless. 

 In cases where nitric aid was used the worm never recovered from the 

 treatment, and in a few cases where the worms were kept for a few 

 days they autotomized the posterior and middle sections. This method 

 was used where only a nerve bridge was desired between the active 

 anterior and posterior parts, as in measuring the speed of transmission 

 of impulses in the nerve cord. 



STATE OF THE ANESTHETIZED AREA 



For a very short period after treatment, the anesthetized section 

 looks whitish and gives off a great deal of mucous, but later the appear- 

 ance is much the same as that of the rest of the worm, except for an 

 increase in diameter. As the worm begins active movement, this 

 middle piece decreases in diameter, due to stretching, for it acts much 

 like a rubber band, extending and then contracting with each creeping 

 movement. However, no waves of muscular contraction run along 

 its length, as in the anterior and in the posterior parts, or from the 

 former to the latter. 



Stimulation of a quiescent worm in the anesthetized and live 

 regions respectively gives a marked difference in response. If the 

 anterior part is touched lightly the response is an increase in diameter 

 due to a reflex stimulation of the longitudinal muscles, but a stimu- 



