58 Buchanan 



manently impaired.^ Thus, at the end, in such an experiment as 56 R, 

 the whole reflex discharge was producing a stronger electrical efltect in 

 the muscle than the artificial stimulus to the nerve could produce, whether 

 or not more fibres were in play, and in neither case (probably) all being 

 in play. As Exp. 45 went on, the reflex eflect as well as the direct 

 efiect got weaker, as may be seen by comparing curves C and A in 

 fio". 8, the eflfect of the strychnine, if I am right in my interpretation, not 

 being great enough in this preparation to overcompensate for a reduction 

 in the number of efferent nerve fibres, and consequently of muscle fibres, 

 which were in play.'^ 



The comparison of the crossed-reflex responses, among themselves even, 

 in Exp. 55 suggests a further differentiation of synapses belonging to one 

 and the same set ; only it appears to me more probable that the set differ- 

 entiated in this case was that of the secondary synapses, and that the 

 agent which differentiated them was fatigue. A glance at the table on 

 p. 45 shows how much the extra delay in the case of the crossed reflex 

 was reduced by an extra few minutes' rest each time this was allowed. 

 The examination of the records brings out certain peculiarities in the four 

 responses referred to by the ff, one of which is reproduced (fig. 11, D), 

 which are not presented by the other crossed-reflex responses. The fact 

 that in all of these the total cord delay was almost the same, and 10-13a- 

 longer than it was in most of the other crossed responses, suggests a further 

 inference, the discussion of which, I will, for the present, postpone. 



Results such as these, and others obtained in the few experiments which 

 have hitherto been made with stimuli not far from the threshold value in 

 strength, seem to me to indicate that it will be more fruitful for the further 

 investigation of processes occurring within the central nervous system to 

 continue to use weak stimuli rather than strong ones. At the same time 

 it must not be forgotten that the experiment in which stimuli nearest to 

 the threshold value were used [Exp. 55] was one of those in which the 

 circulation was not quite normal, and that some of the peculiarities in the 

 responses may be due to the effect which defective circulation has been 

 shown to have in lengthening cord delay, this being probably greater (see 

 p. 26) on some of the synapses than on others. 



We have seen that one of the first actions of strychnine on the cord 

 delay, in the case of the same-limb reflex (on the time taken, if we may 

 so consider it, to pass the primary synapse), is to somewhat shorten it. 



1 In those cases in which the direct effect was weakened by a change in the direction 

 of the current (see p. 16), the reflex effect again usually retained its full strength. 



2 Another interpretation of the regularly recurring difference occasionally met with 

 between the two kinds of reflex eft'ects in the muscle would have suggested itself if the 

 fibres of the gastrocnemius were supplied, as are those of the sartorius and certain other 

 muscles of the frog, by more than one efferent nerve fibre ; but Sandemann (A. f. 

 (Anat. u.) Physiol., 1885, p. 246) has shown that this is not the case, or rather he has 

 shown that each filare of the frog's gastrocnemius is provided with but one motor nerve 

 end-organ, which makes it improbable that it should be the case. 



