NERVOUS SYSTEM OF ANTEDON EOSAOEUS. 529 



at rest for an hour the arms were irritated one by one ; each 

 arm responded readily and extensively to the stimulation, but 

 the movement was limited to the arm directly irritated^ none 

 of the other arms sharing in it, except sometimes the other 

 arm of the pair to which the irritated arm belonged. 



This experiment shows that the physiological connection 

 between the arms can be destroyed by removal of the central 

 capsule and of its branches including the pentagonal commis- 

 sure. After this operation the several arms, with the exception 

 of the two of each pair, are physiologically isolated from one 

 another. The experiment yields identical results whether the 

 visceral mass be present or not. 



I have found it very necessary after severe operations to 

 allow sufficient time for recovery from shock before experi- 

 menting further, and through failure to observe this precaution 

 I obtained at first several very contradictory and perplexing 

 results. From half an hour to an hour I usually found to be 

 sufficient. 



E. On the Functions of the Axial Cords. 



Experiments on the functions of the axial cords and their 

 branches fall naturally under two heads, i. e. those concerned 

 with the relations of these structures to sensation and to motion 

 respectively. 



I propose to commence with the former of these, though 

 as it sometimes happens that the same experiment is concerned 

 with both sensation and motion, it will not be advisable to 

 draw too sharp a line between the two divisions. 



Experiment 10. — Various parts of the surface, both of the 

 disc and the arms, of active uninjured specimens were irri- 

 tated, both mechanically and chemically, in order to determine 

 the normal distribution of sensation. All parts of the surface 

 were found to be sensitive, but in very unequal degrees. Irri- 

 tation of the dorsal surface of the calyx caused only slight 



