74 



Sherrington 



stimulus. Weak reflex relaxations come thus to have a hesitant character, 

 very obvious even to simple inspection. This hesitant character constitutes 

 a point of likeness between weak inhibitory and weak excitatory reflexes ; 

 examples of the latter have been furnished elsewhere.^ 



The myogram of the inhibitory reflex differs from that of an excitatory 

 reflex in the former's showing little or no recovery by the muscle (under 

 the conditions of experiment) of the length it had prior to initiation of the 

 reflex. Subsequent to the inhibition-reflex the muscle continues to remain 

 of the new length it assumed under the relaxation due to the reflex- (fig. 4). 

 After an excitatory reflex the muscle fairly quickly resumes the length it 

 had before its reflex contraction. 



The amplitude of the reflex relaxation caused by a single induction 

 shock, although showing regular increase, within certain limits, with in- 



FlG. 



crease in the strength of the momentary stimulus, does not in my experi- 

 ence reach, even under the strongest of such momentary stimuli, the extent 

 it attains when, instead of a single induction shock, a short series is delivered, 

 as in faradic stimulation (fig. 7, A and B). The extent of the reflex relaxa- 

 tion which a faradic stimulus, even far below maximal, can produce exceeds 

 the relaxation which a maximal single induction shock produces. This 

 constitutes a further point of resemblance between reflex inhibition and 

 reflex excitation. The most ample and powerful of the reflex contractions 

 elicited by the single break shocks (figs. 1 and 2) fall in amplitude and 

 strength much below reflex contractions easily elicitable from the same 

 preparation by faradic stimuli, even brief and quite submaximal. Fig. 7 

 exhibits in A the reflex relaxation of vasto-crureus evoked by a single 

 break shock of 12,000 units of the Kronecker scale. Fig. 7, B, is the reflex 



Sherrington, C. S., Proc. Eoy. Soc, vol. Ixxvii. B, p. 494; Integral. Action etc., 



p. 70. 



Sherrington, C. S., Proc. Roy. Soc, vol. Ixxvi. B, p. 273. 



