270 



A. J. Carlson. 



The method of measuring the rate of propagation of the nerv- 

 ous impulse through this nerve-cord was essentially the same as 

 that employed by Dr. Jenkins and myself in the similar work on 

 the ventral nerve-cord of worms. ^ The preparation and arrange- 

 ment of the animal for the experiment are shown in the diagram 

 in Fig. I. The centipede was placed with its dorsal side next 

 to the platform or removable floor of the moist-chamber and se- 



E / El 



I I /^ 



3 



Fig. I. 



Diagram illustrating the method of measuring the rate of propagation of 

 the nervous impulse in the ventral nerve-cord of centipedes. A, friction wheel; 

 B, pins fixing one end of the reacting portion to the platform; E, electrodes; 

 L, recording-lever; P, platform or floor of moist-chamber. 



■cured to the board by pins, care being taken not to injure the nerve- 

 cord. In Scolopendra morsitans and Scolopocryptops sexpinosus 

 three or four segments are sufl'icient as reacting or contracting 

 portion, in the long and very slender centipede Himantarium taen- 

 iopse"^ eight to ten segments must be used, while in the millipede 

 {Jules sp.), in which the actual lengthening or shortening of 

 any part of the body is very slight, eight to ten segments must be 

 employed in order to give sufl'iclent amplitude to the excursion of 

 the recording-lever. The segment next to the reacting portion 

 was fixed to the board by means of two pins in the manner shown 



ijenkins and Carlson, Journal of Comparative Neurology, XIII, p, 259, 1903. 



-These centipedes w^ere identified for me by Mr. R. V. Chamberlin, of Cor- 

 nell University. The centipede Stylolccinus, sp., made use of in studying the 

 reflexes, was identified by Mr. R. E. Snodgrass. of Stanford University. 



