Physiology of Fentral Nerve Cord of Myriapoda. 273 



portion of the body, and for that reason the postero-anterior rate 

 of the nervous Impulse cannot very well be determined with the 

 present method. 



In the centipedes Scolopendra and Scolopocryptops a single in- 

 duced shock of moderate intensity applied to the nerve-cord either 

 at the anterior or at the posterior end of the body produces con- 

 traction of every segment in the body. In the work on these ani- 

 mals the break induced shock was therefore used as the stimulus. 

 This reaction to the single induced shock is not obtained in the 

 long and slender centipede Himantarium or in the millipede. In 



Fig. 4.— Scolopendra. 



Tracings of the contraction of the anterior segments on proximal and dis- 

 tal stimulation of the cord. Length of cord, 4.5 cm. Transmission time of the 

 impulse, 0.03 sec. Rate, 1.50 m. per sec. Time, 100 d. v. per sec. 



Himantarium a single induced shock ev^en of very great intensity 

 applied to the anterior or posterior end of the nerve-cord does 

 not always produce a contraction that extends over the whole ani- 

 mal. The contraction extends further from the point of stimu- 

 lation the stronger the induced shock, but rarely from one end of 

 the animal to the other. When the cord is stimulated with three 

 or four weak induced shocks that follow one another in rapid 

 succession the contraction involves every segment in the body. 

 In the experiments on this centipede short series of the interrupted 



