REVERSAL OF INHIBITION BY ATROPINE. 243 



the terminal combs of the prolegs, simultaneous extension of the 

 proleg pair, and their apposition the whole movement giving an 

 effective embrace of a leaf margin. The muscles governing the 

 extension of the terminal combs, those having to do with the 

 movements of the prolegs themselves, and the muscles of the body 

 wall, 13 all are involved in this coordinated movement of response 

 to stimulation of the ventral body wall ; and under atropine the 

 movement is entirely reversed combs are retracted, prolegs 

 greatly retracted, body wall itself retracted rather than, as nor- 

 mally, protruded in the region between the proleg. This " re- 

 versal " was found only in connection with the prolegs, never with 

 the thoracic legs. 



Normally, lightly touching a proleg comb, or the skin between 

 the prolegs, leads to extension of both members of the pair ; then 

 a subsequent light touch leads to the usual clasping motion ; under 

 atropine, touching comb or skin between prolegs results in the 

 spreading apart and deep retraction of the prolegs. The reversal 

 of the proleg response persisted for 20 hours or more. 



Atropine is very effective in producing heightened irritability; 

 and usually there was evidence, also, of a tendency to dorsal con- 

 tracture slight suggestion of an opisthotonic state (perhaps re- 

 lated to the lifting of the head when the normal animal is disturbed 

 on a leaf). 



In one or two cases transitory evidence of proleg reversal was 

 obtained during observation of larvae injected with nicotine solu- 

 tions, and particularly with pilocarpine; it could not be produced 

 at will with these substances, however, nor was trace of the phe- 

 nomenon detected under treatment with a variety of other neuro- 

 phil drugs. It is a characteristic and pronounced effect peculiar, 

 in my experience, to atropine. 



With strychnine, and less clearly with atropine, suggestion was 

 had of the special stimulation of the dorsal muscles ("opistho- 

 tonus "). This effect is not specific, or at least is not so specific as 

 the proleg reversal. Tetraethylammonium chloride (1)1/64) in- 

 variably led to striking opisthotonic spasms, due chiefly to con- 

 traction of dorsal muscles at the thoracic level. Chloroform (one 

 third saturated) behaved somewhat in the same way, but more 



is Cf. Peterson, A., Ann. Ent. Soc. Amer. Vol. V., p. 246, 1912. 



