REVERSAL OF REACTION BY MEANS OF STRYCHNINE IN 

 PLANARIANS AND STARFISH. 



By a. K. MOORE. 



{From the Physiological Laboratory of Rutgers College, New Brunswick, N . J.) 

 (Received for publication, June 20, 1918.) 



Experiments on the Planar ian, Bdelloura. 



It has been shown that a single excitation at a median point in the 

 earthworm eHcits a shortening of the body anterior and a lengthening 

 posterior to that point. Active extension of the body is produced by 

 contraction of the circular muscles, and by inhibition of contraction of 

 the longitudinal muscles of the body. This is a case of reciprocal 

 innervation. 1 Further, it has been found that in the earthworm, just 

 as in vertebrates, strychnine converts inhibition into excitation, thus 

 causing upon stimulation a contraction of the longitudinal muscles, 

 which results in a shortening posterior to the point of stimulation. ^ 



Flatworms have, in addition to longitudinal and circular systems 

 of muscles, transverse muscle fibers. These, with the circular 

 muscles, cause an increase in length and decrease in width and thick- 

 ness of the animal upon contraction, while the shortening and 

 thickening characteristic of the quiescent position are necessarily 

 associated with a contraction of the longitudinal musculature 

 and a relaxation of their antagonists. This implies also reciprocal 

 innervation. 



In order to determine whether the nervous mechanism in flatworms 

 is similar in its reaction to that of the earthworm, the following experi- 

 ments were made with specimens of Bdelloura. This is a marine 

 flatworm, ectoparasitic on Limulus. If an active individual is touched 

 with an instrument such as a pair of forceps, it stops locomotion, 

 shortens and thickens; i.e., the longitudinal muscles contract and the 

 circular and transverse muscles relax. In case the animals are first 



1 Garrey, W. E., and Moore, A. R., Am. J. Physiol., 1915, xxxix, 146. 



2 Knowlton, F. P., and Moore, A. R., Am. J. Physiol., 1917, xliv, 490. 



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