Physiology of Ventral Nerve Cord of Myriapoda. 271 



In Fig. I, so that the contractions of the body anterior to this 

 point could not be communicated to the lever. The freeing of 

 the nerve-cord for the application of the distal and proximal elec- 

 trodes is a very difficult undertaking, and in no instance was it 

 done as completely as indicated in Fig. i, especially in the slender 

 Himantariiim, in which the nerve-cord is correspondingly slender, 

 and in the millipede, in which the dissection is rendered difficult 

 by the very thick chitenoid epidermis. The dissection for the 

 proximal electrodes was in every case made at least two or three 

 segments from the reacting portion of the body, to avoid escape 

 of the current directly to the reacting musculature. In Himan- 



§mm 



Fig. 2. — Scolopendra. 



Tracings of the contraction of the posterior segments on stimulation of 

 the cord at the distal and the proximal points. Length of cord, 5cm. Trans- 

 mission time of the impulse, 0.02 sec. Rate, 2.50m. per sec. Time, 100 d v. 

 per sec. 



tarium six to ten segments were allowed to intervene between the 

 point of stimulation and the reacting portion. 



No anaesthetics were used, but prior to fixing the animal to 

 the platform the head segment, including the cerebral ganglion, 

 was usually removed. 



The posterior or tail segments of the decapitated centipede 

 which has been fixed to the board and prepared in this manner 

 usually become quiescent after a few minutes, and remain quies- 

 cent during the intervals between the stimulation of the cord, 

 provided the tension from the recording-lever is not too great. 



