26 Buchanan 



produces its maximal electrical effect) is only at all commonly present in the 

 responses of those preparations in which not only the cord but the circula- 

 tion was affected by the drug, and in which (perhaps, to some extent, 

 conse(|uently ^) all the muscles were in spasm, and in which cord delay (to 

 all strengths of stimulus) was longer than in normal, and still more so than 

 in lightly strychnised, preparations. What strychnine acting on the cord 

 alone effects, appears to be counteracted in certain respects by what strych- 

 nine acting on the circulation, and hence indirectly on the cord, effects. We 

 have seen that this is the case as far as cord delay is concerned in the 

 reflex we have so far been considering. It will be still more striking in 

 the reflex we shall next have to consider, and for this second more complex 

 reflex we shall see this conflict between the direct and indirect effect of 

 strychnine on the cord showing itself perhaps in another way also. The 

 cord of the decerebrate frog used in Exp. 55 had been for some hours under 

 the predominating influence of the indirect action of strychnine. By the 

 time the preparation was made, that effect showed signs of wearing off, and 

 it would appear that the more specific action of the drug upon the cord — 

 the lowering of the threshold at any rate — was beginning to re-assert itself, 

 but it had only as yet done so for some of the synapses concerned in the 

 response of this particular muscle, whatever it may have done for others, or 

 possibly the same, synapses concerned in the responses of other (e.g. anta- 

 gonistic) muscles.- The fact that the temperature of the room was rising 

 while this experiment was being made probably contributed to bringing 

 about variability of threshold, since there can be no doubt that strychnine 

 is much more effective at higher temperatures than at lower. 



A record such as the one reproduced in fig. 11, C, seems tome, therefore, 

 to show that synapses with higher resistances, i.e. those which required a 

 stronger afferent stimulus to be forced at all, took longer (up to as much as 

 20o- longer) to be passed by impulses hardly above their threshold values in 

 strength than did those with lower resistances for which an afferent 

 stimulus of the same strength would have a higher value ; and that thus 

 variations produced in the thresholds of the structures excited have given 

 us information that we could not succeed in obtaining by altering the 

 strength of the exciting stimulus. The question, however, as to whether we 

 may apply this information to a more normal, even though strychnised, 

 animal, remains. It may be that it is only in an animal with circulation 



1 I would here refer to Bethe's observations, in which •' Erstickungskrampfe " (p. 248), 

 " welche sich von Strychnmtetanus nicht unterscheiden lassen " (p. 247), are obtained in frogs 

 under conditions which he regards as signifying increased consumption, and therefore 

 requirement, of oxygen (Eosenthal's Festschrift, 1906). 



2 It may well be that this want of co-ordinate action of the synapses concerned in the 

 contraction of one muscle, which seems so often to prevail when strychnine spasms are at 

 their height (I have other examples of the phenomenon indicating it in records taken 

 years ago), is correlated with the opening of paths to other muscles which are normally 

 closed by the high resistance of the synapses or the ]jarts of the synapses (if we regard as a 

 whole synapse, the boundary, or gap, between all the afferent fibre-terminations, and the 

 one motor cell they adjoin) concerned in their contraction, and normally obtaining when 

 the resistance in the first synapses, or parts of synapses, was low. 



