240 ^'. J. CROZIER. 



Since strychnine has been relatively unique among neurophil 

 substances in producing effects of the kind specified, it is desirable 

 to call attention to the fact that among insects (caterpillars) phe- 

 nomena identical in their nature with the reversal of inhibition 

 typically induced by strychnine may be produced through the 

 action of atropine ; whereas, with these animals, strychnine is sin- 

 gularly ineffective and in fact fails to produce " reversal of in- 

 hibition." This point is important for the conception of pro- 

 gressive chemical differentiation of the nervous system in the 

 animal series. Moreover, it raises certain difficulties in the way 

 of employing strychninization as a test for the presence of synaptic 

 structures or their homologues ; 10 but further study is required to 

 permit discussion of this aspect of the matter. 



The experiments had in view the general impression that insects 

 (and other arthropods) are peculiarly resistant to strychniniza- 

 tion. 11 A common method of testing the action of a drug has 

 been to submerge the organism in an appropriate solution, or to 

 introduce the material into the alimentary canal. The cuticula of 

 arthropods, however, may seriously interfere with such trials ; its 

 permeability is but little understood. Similarly, with Ascaris 

 Schroeder 12 reported that immersion for three hours in 0.5 per 

 cent, solution of strychnine was without effect; but some time. ago 

 I observed that characteristic squirming movements could be in- 

 duced by injecting weak strychnine solutions into the interior- of 

 the body. 



Resort was accordingly had to hypodermic injection. With 

 small insects such procedure is impracticable; moreover, it was 

 desirable to use forms in which the nervous system had not under- 

 gone great condensation. Suitable material was found in certain 

 large caterpillars, of which five species were employed : Protoparce 

 celeus, Samia cyntJiia, S. promcthia, Aut omens io, and Ceratoinia 

 catalapce. The last named was not quite so well adapted to the 

 injection as were the first four, upon which most of the observa- 

 tions were made. Half-cubic-centimeter volumes of solution 



10 Parker, G. H., " The Elementary Nervous System," Philadelphia, 229 

 pp. 1920. 



11 Biberfield, J., Ergebn. Physiol., Jahrg. 17, p. 175; and the fact is well 

 known to economic entomologists. 



12 Schroeder, W., Arch. Exp. Path. u. Pharm., Bd. XIX., 290, 1885. 



