32 Buchanan 



like, call it), may therefore be postponed until the results obtained from my 

 own experiments on strychnine frogs have been stated. To these we may 

 now turn. 



Even in preparations in which the excitability of the cord has been 

 raised by strychnine sufficiently to make certain of the presence of the 

 same-limb reflex effect in the records of the electrical responses, it is by no 

 means certain that a reflex effect will be also obtainable when the nerve 

 of the opposite side is stimulated by a single break induction shock. There 

 is, however, every likelihood of obtaining a response to such a stimulus 

 when the strychnine has been allowed a certain time (varying with tempera- 

 ture, season, dose, etc.,) to act, and there is hardly Siny doubt about obtaining 

 it in a preparation which has been injected several hours before and is 

 either still showing in its attitude all the external symptoms of strychnine 

 poisoning, or has begun to recover. 



The crossed-reflex response has been recorded in sixteen preparations, 

 many of which have already been referred to in connection with the same- 

 side reflex. In all, the scia tic nerve of the opposite side was prepared, usually 

 before beginning the experiment, in exactly the same way as its fellow, 

 and a second pair of needle electrodes was applied to it. A Pohl reverser 

 without crossed wires in the secondary circuit made it easy to excite the 

 two nerves alternately. 



The measurements obtained from the records of the several responses, 

 and the probable cord delay estimated therefrom in each, are given for 

 thirteen of the experiments on the right-hand side in the tables beginning 

 on p. 35, which are so arranged that the time, measured and estimated, 

 in any crossed-reflex response may be readily compared with that, measured 

 and estimated in the same way, in the same-side reflex response, recorded 

 immediately before or after it, and given on the left-hand side. 



In order to estimate the cord delay when the nerve of the opposite side 

 was stimulated, I have subtracted from the whole measured time, firstly, the 

 time known, from the measurement of the same-limb reflex record, to be 

 taken by an impulse to reach the recording spot on the muscle directly (i.e. 

 through the motor part of the nerve) from tlie near anode, and, secondly, 

 the time which would have been taken to traverse the measured length of 

 nerve from the far anode to the near one, on the assumption that it 

 travels at the rate of 30 metres per second. The first of these time values 

 would be the same as when the same-limb reflex was recorded, provided that 

 there had been no obstruction at the kathode to be overcome at the time this 

 was taken, in which case allowance would have to be made for the fact. The 

 second of these time values would also be very nearly the same in the two 

 kinds of responses, the distance up one nerve and down the other as far as 

 the near anode being, if the needles were on corresponding parts, just about 

 the same as the distance from the near anode to the cord and back, and 

 the time taken to traverse it only being different if very strong ascending 

 currents were being used. In the last column of the table, I have given 



