"REVERSAL OF INHIBITION" BY ATROPINE. 241 



could be injected without material loss of fluid through the punc- 

 ture; sealing the puncture with celloidin, after withdrawing the 

 injection needle, was found unnecessary, and indeed undesirable, 

 as leading to local irritation. Strychnine injection was usually 

 made laterally at about the level of the first prolegs; the needle, 

 pointing anteriorly, was thrust through the cuticule of an inter- 

 segmental constriction. It may be stated at once that the level of 

 the injection appeared not to influence the outcome. 



Upon the injection of strychnine sulphate in concentrations less 

 than i : 100 no efforts could be detected, beyond a momentary loss 

 of the ability to creep ; this was not specific and could be induced 

 by injecting distilled water or Ringer solution. Protoparce celeus 

 and other forms were observed to drink as much as 0.8 cubic 

 centimeter or more of i per cent, strychnine sulphate. 



In Automcrls io injection of 0.5 c.c. of i per cent, strychnine 

 sulphate led to twitching contractions of the abdominal muscu- 

 lature, sometimes symmetrical, sometimes better developed at one 

 side; the legs and prolegs were quiescent, nonreactive to stimula- 

 tion, and the prolegs particularly were pressed together. After 

 4 minutes a pinched proleg retracted its terminal comb, but no 

 further response was observed; the body musculature was very 

 "flabby." At about io minutes subsequent to injection there 

 appeared a phenomenon, only partially reproduced with the other 

 species, which is the most closely related among those observed to 

 the " typical " strychnine effect. With the animal on its side, the 

 body may be bent somewhat, either dorsally or ventrally. If the 

 caterpillar be given a slight ventral flexure, rhythmic twitchings 

 appear in the dorsal thoracic zone, which serve to make the body 

 curvature distinctly concave dorsally ; whereas, with a dorsal curva- 

 ture initially impressed, the caterpillar remains in that position, 

 although the dorsal twitchings persist. The twitchings of the 

 dorsal muscle bands likewise continue when the larva is picked up 

 by its posterior spine. 



The stimulation of the contraction of dorsal muscle bands is 

 similar to the stimulation of dorsal extensor muscles in other 

 groups, but further evidence of characteristic strychnine action is 

 lacking. It is probably significant that Automeris io is distinctly 

 the most reactive, most " irritable," of the caterpillars studied. 



