24 Buchanan 



very marked under the influence of ^ strychnine. It is therefore at first 

 sight somewhat surprising to find that the measurements of my records, 

 examples of which are given in the protocols on pp. 35 to 48, give no more 

 evidence of cord delay varying with strength of stimulus than do 

 those obtained with normal cords. Thus, while in six experiments [16, 40, 

 first part of 42 (p. 28), 46 (which, however, was one of those in which the 

 records give so little evidence of the presence of strychnine), 52, and 53] 

 made with the streng-th of the induction current kept constant throughout, 

 the cord delays varied in successive responses by as much as from 2(t to 4(7, 

 they varied hardly at all in five other experiments [14 L, end part of 42, 

 47, 49 R, and 56 R] made with the strength of the stimulus varying a good 

 deal, even though, as in the three last of these, the strengths used to obtain 

 some of the responses cannot have been much greater than just sufficed to 

 produce a reflex effect at all. It is true that in 56 L the one response 

 recorded with the weakest stimulus had the longest cord delay (l-2o- 

 longer than the rest), and it is also true that in Exp. 14 L (see p. 21) a strong 

 stimulus did on one occasion evoke a response in a time that was 2(t shorter 

 than it was on any other occasion ; but these are isolated records, and in 

 Exp. 14 L a stimulus equally strong was applied on three other occasions 

 without the delay being shorter than it was with weaker stimuli. 



My records, therefore, furnish no evidence of an inverse relationship 

 between cord delay and strength of stimulus, even in preparations in which 

 the effect of strychnine on the cord is well marked, so long as the 

 strength has a certain value which is not far above the threshold 

 value. The strength may be doubled, trebled, or even increased to four 

 or five times its value without altering the cord delay (see footnote 

 to p. 54). But although there can be no doubt as to what is the case with 

 stimuli above a certain strength in relative value, we find ourselves on far 

 less certain ground when we try to discover experimentally what happens 

 when the strength of the stimulus is almost at its threshold 

 value. For here we are met with difficulties as great as those met 

 with in making the same investigation in the normal cord, although they 

 are of another kind. While strychnine cords have undoubtedly so far the 

 advantage over normal ones, for the investigation of the influence, if any, 

 exerted by this and other physical conditions, that any one of them will 

 give as a rule a comparatively large number of responses, they have this 

 disadvantage for the investigation of the particular question as to the 

 influence of strength of stimulus, that the threshold value, i.e. the strength 

 of the stimulus just sufficient to produce an effect, is apt to change during 

 the experiment. This was the case most strikingly in Exp. 55, in which 

 stimuli at first too weak to produce any effect at all became capable of 

 doing so in the course of the experiment. The cord delay, as the table 

 shows, varied throughout a good deal in the diflferent responses, but did 

 not do so in any definite regular relation to the strength of stimulus 

 evoking them, near as this must have been at times to the threshold value. 



