Comparisons between Reflex Inhibition and Reflex Excitation 71 



quick succession from a preparation that has previously lain quiescent for 

 some length of time. The staircase phenomenon seen in skeletal and 

 cardiac muscle may then make its appearance in the reflexes (fig. 3).^ 



Turning to the inhibitory side of the reflex, the reactions exhibit there 

 a grading not less delicate and extensive than those of the excitatory side. 

 With increase in the strength of the stimulus (break shock), the amplitude 

 of the reflex relaxation increases (fig. 4). Also the speed of the relaxation 

 becomes greater (fig. 4). Increase in speed of progress of the relaxation 

 is particularly evident when, instead of a single momentary stimulus, the 

 stimulus used is faradic. Fig. 5, A B C, illustrates this. For each of the 

 three reflexes in the figure the stimulus consisted of a series of double 

 shocks obtained by an iuterruptor vibrating 40 per second in the primary 

 circuit. In the reflex of fig. 5, A, the secondary coil stood at 40 units on 

 the Kronecker scale ; in reflex B at 100 units ; in reflex C at 500 units. The 



reflex relaxation is not only greater in B than in A, but its progress is more 

 rapid ; and in C than in B. This greater speed of progress of the relaxa- 

 tion under stronger stimuli finds a close counterpart in the greater speed 

 of augmentation of contraction in the excitatory reflex under stronger 

 stimuli.^ It is a point of likeness between the inhibitory and the excita- 

 tory sides of this "flexion-reflex." The relaxation in reflex C (fig. 7) is 

 followed, after a latency longer than that of the initial reflex inhibition, 

 by the contraction termed the "rebound-contraction,"^ ascribable to "suc- 

 cessive spinal induction." * That this occurs in C and not in B or A is in 

 accord with the description of the phenomenon given elsewhere,^ and with 

 the explanation there oflered. 



When the inhibitory relaxation is weak it is, in my experience, not 

 rarely accompanied by tremor. This is seen in fig. 5, A and B, ; also in the 



1 Cf. Stirling, W. (in the frog), op. cit. 



2 Sherrington, C. S., Proc. Roy. Soc, Ixxvi. B, pp. 272, 274. 



3 Sherrington, C. S., Proc. Rov. Soc, vol. Ixxvi. B, p. 160, 1905 ; ibid., Ixxvii. B, 

 p. 478, 1906 ; ibid, Ixxix. B, p. 347, 1907 ; ibid., Ixxx. Integrat. Action etc., ]k 206. 



* Ibid. 5 Ibid. 



