Vol. XLIII. October, 1922. No. 4. 



BIOLOCxICAL BULLETIN 



"REVERSAL OF INHIBITION" BY ATROPINE, IN 



CATERPILLARS. 



W. J. CROZIER, 

 ZOOLOGICAL LABORATORY, RUTGERS COLLEGE. 



\Yith a variety of invertebrate animals it has been found that 

 strychnine exerts upon the neuromuscular structures an effect 

 essentially similar to that which it displays in connection with the 

 synapse-substance of vertebrate central nervous organs namely, 

 a decreased resistance to transmission, resulting in enhanced re- 

 activeness ; and a selective excitation of extensor elements, leading 

 to opisthotonic curvature and to " reversal of inhibition " in re- 

 sponses involving reciprocal innervation. Representatives of the 

 following groups are known to show behavior of this type under 

 strychninization, and must therefore be accorded as a common 

 property the possession of strychnine-receptive complexes suitably 

 situated in their nervous organs : Platyhelminthia (Planaria, 1 

 Bdclloura-} ; Mollusca (Ch&to-pleura? Chromodoris* Liina.r, 1 

 Onchidium, 5 Loligo 5 } ; Echinodermata (Thyone, 7 Asterias*) ; An- 

 nelida (earthworm, 9 leeches 1 ). 



1 Personal observation. 



2 Moore, A. R., Jour. Gen. Physiol., I., p. 97, i< 18. 



3 Crozier, W. J., Jour. Gen. Physiol., II, p. 627, 1921. 



4 Crozier, W. J., and Arey, L. B., Jour. Exp. Zodl., Vol. XXIX., p. 261, 1919. 



5 Crozier, W. J., and Arey, L. B., Jour. Exp. Zodl., Vol. XXXII., p. 443, 

 1921. 



6 Moore, A. R., Jour. GeM. Physiol. , Vol. I., p. 505, 1919. 

 " Pearse, A. S., BIOL. BULL'., Vol. XVIII., p. 42. 



s Moore, A. R., Jour. Gen. Physiol., Vol. II., p. 201, 1920; Jour. Pharm. 

 Exp. Therap., Vol. IX., p. 167, 1916. 



9 Knowlton, F. P., and Moore, A. R.. Amer. Jour. Physiol., Vol. XLIV., 

 P. 490. 



239 



