88 Journal of Comparative Neurology and PsyeJiology. 



To make sure that the point of peripheral stimulation was 

 the same in the extended and the contracted condition of the 

 nerve the point of union of one of the branches with the main nerve 

 trunk w^as chosen and this point marked with a bit of carbon 

 from the drum which adhered firmly through the experiments. 

 Since the central point of stimulation was in every case nearer 

 the pedal ganglion it was easily kept the same in the two con- 

 ditions. Although in each of these i6 slugs the nerve was 

 stretched to about twice the length exhibited in the contracted 

 state, in no case was the nerve stretched sufficiently to give rise 

 to an impulse, and it is therefore probable that the degrees of 

 extension of the nerve were within the range employed by the 

 animal in its normal movements. After a second or third repe- 

 tition of the stretching, the nerve did not always contract to the 

 length first assumed, although freed as much as possible from 

 the restraining force. This was probably due mainly to the 

 viscid mucus in the body cavity which stuck to the nerve more 

 or less and by slightly hardening on exposure to the air, offered 

 some resistance to its contraction. 



Of the sixteen experiments three typical ones are given in 

 detail, the remainder only in summary. In this summary (table 

 IV), the "length of nerve," the "transmission time" and the 

 "rate" represent the averages calculated from the individual pairs 

 of records in the stretched and contracted condition of the 

 nerve. Fig. i gives a typical series of the tracings obtained 

 from four successive pairs h'om alternately extended and con- 

 tracted condition of the same nerve respectively. 



A study of these tables shows that there is practically no 

 difference in the actual rate of the nervous impulse in the 

 stretched and the contracted condition of the nerve ; the in- 

 crease in the latent period of the stretched nerve is caused by 

 the additional length of the nerve. In nine of the experiments 

 (Table IV. Nos. i, 2, 4, 5, 6, 7, 9 and 12) the average rate in 

 the stretched nerve is slightly less than that in the contracted 

 nerve, but, as will be seen from Table I, in these series, indi- 

 vidual pairs of records are found which show the reverse. In 



