ON THE TIME TAKEN IN TRANSMISSION OF REFLEX IM- 

 PULSES IN THE SPINAL CORD OF THE FROG. By 

 A. D. Waller. 



(Received for p^Mication I4th July 1908.) 



The observations of Miss Buchanan on the time taken in transmission of 

 reflex impulses in the spinal cord of the frog have reminded me of some 

 experiments I made on this subject in 1884, the conclusions from which are 

 in some respects similar to those drawn by Miss Buchanan. In other 

 particulars the facts respectively observed by Miss Buchanan and by 

 myself supplement each other, obtained as they have been by different 

 methods, and altogether independently. 



Miss Buchanan used the capillary electrometer, so that the reaction in 

 only one limb at a time could be recorded ; I used a double myograph, so 

 that the reactions in two limbs to the same stimulus were simultaneously 

 recorded. 



The two methods are indeed complementary of each other, each atibrding 

 information of its own not afforded by the other. I must say, however, 

 that as regards one principal item — the comparison of delays of \'arious 

 kinds of reflexes — it appears to me that the electrical method followed by 

 Miss Buchanan is distinctly inferior to the mechanical method of which I 

 made use. By the former plan the comparison has to be established between 

 successive individual effects, and individual differences of time are not out 

 of the question, whereas by the latter it is easy to obtain for comparison the 

 simultaneous effects of two different kinds of reflex contraction. 



The two points in Miss Buchanan's results that have most aroused my 

 interest in connection with my own results are : 



1. The prolongation of reflex time in consequence of the action of 

 strychnine on the spinal cord. 



2. Tlie fact that the cord delay is roughly about twice as great for a 

 crossed as for an uncrossed reflex, and the inference therefrom that there 

 are normally two spinal synapses interposed in a crossed path and a single 

 synapse in any uncrossed path. 



In my own experiments the points that seemed to me to be most note- 

 wortliy were : 



1. The excessive prolongation of reflex times after strychnine injection. 



2. The consequent dissociation that can be distinguished of the com- 

 ponent parts of which crossed and uncrossed reflexes are made up. 



