188 THE ELEMENTARY NERVOUS SYSTEM 



end. Such a preparation had the shape of a letter V, with 

 two half hydranths at the free ends of the V and the un- 

 severed base at the angle (Fig. J4). On stimulating one 

 half hydranth with a faradic current both arms of the 

 preparation contracted though the base was outwardly 

 inactive. Hence it was concluded that the base, though 



without muscle, trans- 

 mits nervous impulses 

 from one side of the 

 polyp to the other. If the 

 base is now locally anes- 

 thetized and the experi- 

 ment repeated, the con- 

 traction is found to be 

 limited to the arm of the 

 preparation that is stim- 

 ulated, thus demonstrat- 

 ing the superficial loca- 

 tion of the transmitting 

 tissue. 



Another form of this 

 experiment was next 

 tried, in which, however, 



the two arms of the preparation were united through the 

 hydranth instead of through the base. In this experiment 

 transverse transmission through the hydranth was as 

 easily demonstrated as it had been through the base. 



In a third experiment the stalk alone was used, the 

 hydranth and base having been cut off. When one arm 

 of such a preparation was stimulated the other arm al- 

 most invariably failed to respond, thus showing that 

 though transverse transmission is easily accomplished 

 in the base or in the hydranth, it is not so easily accom- 



Fio. 44. A polyp of Corymorpha split 

 lengthwise except at its aboral end through 

 which transmission may be accomplished 

 from one arm of the preparation to the other. 



