Transuiissioii-tiine of Reflexes in Spinal Cord of Frog 



11 



the real difference of time in this one response, the only one taken with 

 the current descending, was nearer ISo- than 14(r. In the other responses 

 obtained from this preparation (by means of ascending break induction 

 shocks to the nerve), the interval between the two arrivals appeared to be 

 about IGor in two and about 19cr in the third. It was probably slightly, 

 but not so much as lo-, shorter (see p. 14). 



In most of the preparations the interval was between lOcr and 21o-, but 

 in three it was 23o-, and in three others it was longer still. Five, out of 

 twenty-three, of the preparations gave records which showed no sign of 

 any reflex effect ; and in the records obtained with two others, the reflex 

 effect, though represented in some, was too small for the place at which 

 the curve began to alter its course to be determined with accuracy. 

 Each cord which yielded more than one measurable reflex effect gave it in 

 about the same time in all the responses. In seven preparations from 

 which records of the reflex response were obtained more than once, the 

 recurrence of the same interval (even under different conditions as to strength 

 of stimulus) was very striking. This may be judged of by the measurements 

 obtained from the records in one experiment (the longest of the seven), the 

 conditions obtaining, and the results obtained in which are given here in 

 tabular form. 



Exp. 58. Dec. 17, 1906. Room temp. 12° C. 



' The strength of the current in all the tables is given in units, read off from the 

 graduated scale of the Kronecker indnctorium, 1 Daniell being in primary circuit, 60,000 

 ohms in secondary. With such an arrangement the break inductioti current could not usually 

 be felt on the tongue with strengths under 12,000. 



2 p stands for the proximal leading-oil' electrode. 



^ The length of nerve from tlie i)rincipal exciting electrode to the cord wius not in 

 every case directly measured, althougli the length of the sciatic nerve itself in the thigh 

 was always measured. I ascertained that the ratio of sciatic plexus length to nerve length 

 in a certain number of pre])arations was as 1 to OTB, and have in the majority of crises 

 calculated the length from this. A few millimetres of nerve more or le.ss would make so 



