86 Journal of Comparative Neurology and Psychology. 



does not appear to affect its functional activity. If, however, 

 the nerve was stretched one or two centimeters in excess of the 

 length it reaches in the animal fully extended by its own act of 

 crawling, this excess of stretching itself acted as a stimulus and 

 both the elasticity and irritability of the nerve were speedily 

 lost not to be subsequently regained. It became a matter of 

 interest to determine what is the effect of stretching the nerve 

 on the rate of conduction of the nervous impulse. 



In the time from August, 1901, to May, 1902, the muscle- 

 nerve preparations of 25 individuals, in connection with other 

 work, were tested on this point, and all these showed without 

 exception an increase in the latent period following the exten- 

 sion of the nerve from the contracted state, the height and 

 rapidity of the muscular contraction remaining fairly constant. 

 In order to determine more accurately the relation of the amount 

 of extension of the nerve to its rate of impulse we took a series 

 of records obtained from stimulating the central and peripheral 

 points chosen on the pedal nerve in the contracted condition 

 and in the extended condition. From these records rates for 

 different amounts of extension in the same nerve were deter- 

 mined, allowing comparisons to be made. This series of ex- 

 periments was carried on at the Hopkins' Seaside Laboratory 

 at Pacific Grove in June, 1902. Except for the alternate 

 stretching and relaxation of the nerve, the apparatus and method 

 of experimentation were the same as used in the previous work 

 on the slug. The muscle-nerve preparations from 16 large 

 individuals in good condition were used and it will be seen from 

 the summary in table IV that several pairs of records both in 

 the extended and contracted condition of the nerve were usu- 

 ally obtained from each preparation. 



Fig. I. Ariolmiax columbianiis . Four pairs of successive records obtained 

 on stimulating peripheral and central points in the stretched and relaxed condi- 

 tion of the pedal nerve in the same individual, c. curve from central, /. 

 curve from peripheral point of stimulation. 



No. I. Stretched, length of nerve, 8 cm. rate, 36.8 cm. 



No. 2. Relaxed, " " " 4 cm. rate, 36.4 cm. 



No. 3. Stretched, " " " 8 cm. rate, 33.6 cm. 



No. 4. Relaxed, " " " 4 cm. rate, 30.8 cm. 



