Transmission-time of Reflexes in Spinal Cord of Frog 59 



This action appears to be far stronger on the factor which determines 

 the extra delay in the case of the crossed reflex, i.e. on the time taken 

 to pass the secondary synapse. This time may apparently be ver}- 

 considerably shortened by it. In two preparations, as has been seen, in 

 both of which the drug was taking eflect very quickly, it was reduced in 

 the course of the experiment to bu and 6cr respectively. According to 

 Wundt, it may sometimes be reduced to as little as 4(t. Are we to infer 

 from this, and from the fact that the only time a crossed-reflex response 

 was obtained in a preparation which was hardly influenced at all by the 

 drug [Exp. 38], the delay was as much as 63cr longer than in the cor- 

 responding same-limb reflex response, that the time taken in passing the 

 secondary synapse is in the normal cord a good deal longer than it usually 

 is in the strychnised cord ? I think not, although, if ever I succeed in 

 obtaining and recording the crossed reflex in response to a single in- 

 stantaneous stimulus in a normal preparation, I should not be at all 

 surprised to And that the delay in the manifestation of the effect in the 

 muscle was still longer.^ With regard to its long duration in normal or 

 very nearly normal preparations, I would suggest that the same sort of 

 explanation may apply as applies to the postponement of the moment at 

 which the eflect becomes maximal in the case of some of the responses to 

 just efficient stimuli in fully strychnised preparations. If we compare, for 

 example, the maximal strength of the reflex effect attained in the responses 

 to which fig. 11, C and D, refer, with what it was when it started in these 

 responses, and then compare the maximal strength of the reflex effect in a 

 normal cord as it usually is, and as it was in Exp. 38 (steepness of rise about 

 the same as in the record reproduced in fig. 1, B), with something less than 

 it, in the same proportion (or in the proportion which the crossed-reflex eff'ect 

 sometimes bears to the uncrossed in strychnine preparations, e.g. fig. 6), 

 it is evident that this something, if it existed, would be imperceptible with 

 the recording instrument and arrangements which were being used. 

 Whatever is the explanation of the postponement of the moment at which 

 the eflect reaches its maximum in the one case, seems to me likelj^ to be 

 the explanation of the late appearance of any effect at all in the other case. 

 The postponement in the strychnine preparations, since it may appear 

 in the response of the uncrossed as well as in those of the crossed reflex, is 

 likely to be due, in part and sometimes entirely, to some factor in the set 

 of primary synapses preventing the appearance of the full eflect at once. 

 I have already suggested (p. 27) that this factor is the want of accord in 

 the moment of dischai'ge of the separate cells, brought about by impair- 



1 Since this paper was sent in I have at last succeeded in obtaining in two much 

 cooled but undrugged preparations a trui- crossed-reHex response in the biceps femoris. 

 Although the records of it. were extremely minute, the moment at which it began could 

 be determined. In one preparation the effect appeared after an interval which was twice 

 as long as in the same-limb reflex ; in the other, after an interval which was, both relatively 

 and absolutely, considerably longer. The cord delay in the same-limb reflex was very long 

 (about 50(r) in each preparation. [Nov. 1907.] 



