252 ' Waller 



The inferences which I then drew and still draw differ from those of 

 Miss Buchanan: naturall}', at that time I did not think or speak in terms 

 of " synapses." Speaking in terms of the afferent and efferent aspects of 

 spinal cells, I inferred from the facts under my observation that the delay 

 of reflex action, which increases as the toxic effects of strychnine deepen, 

 is the index of a gradually increasing block of transmission in the spinal 

 cord, and that this block of transmission occurs at first exclusively and 

 later chiefly at the junction of the afferent nerve with the cord. 



I have reviewed this conclusion by a re-examination of the facts upon 

 which it rested, and in the light of Miss Buchanan's experiments, in order 

 to see whether it could be expressed in terms of synapses, and whether the 

 conclusion so expressed was in harmony with Miss Buchanan's conclusion. 



But, firstly, as regards the facts : — I found, as Miss Buchanan did, that 

 the normal time of a simple reflex was approximately yoo^^^ sec, and that 

 of a crossed reflex was approximately j-§„ths. (My actual figures were 

 O'OOS and 0"016.) But, unlike Miss Buchanan, I found that this proportion 

 of 1 to 2 was not maintained in the prolonged times of simple and crossed 

 reflexes observed in strychninised frogs. The times (fig. 3) were, e.g., simple 

 0'038, crossed 0-046, difference 0008 ; i.e. the difference of xoo^^^ ^^^- attribut- 

 able to transverse transmission, or, let us say, to the interposition of a second 

 synapse in the reflex arc, remained unaffected in the presence of a prolonga- 

 tion of time as regards the first synapse of approximately yfo^hs over and 

 above the normal delay of yooth. 



The case of longitudinal transmission lends itself to a similar argument. 

 Fig. 4 of an experiment in which muscular contractions of the arm and of 

 the leg of a strychninised frog were recorded, stimulation (by a single break 

 induction shock) being applied to the skin of the leg, gives the times : simple 

 = 0-060, transmitted = 0-608, difference = 0-008 ; and this normal difference of 

 approximately yjo^'h sec, attributable to longitudinal transmission, or, let 

 us say, to the interposition of a second synapse in the reflex arc, remains 

 unaffected in the presence of a prolongation of time as regards the first 

 synapse of approximately y^^jths over and above the normal delay 

 of j-^^tli- 



I have expressed values in hundredths of a second for the sake of 

 clearness, and for the sake of further clearness I will set out in detail in 

 hundredths, and in terms of the synapse conception, what I consider to be 

 the components of the total delays exhibited in fig. 4. 



