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Prof. C. S. Sherrington. Reciprocal [Mar. 25, 



excitation with any particular value of inhibition results in a grade of con- 

 traction less than that which the excitatory stimulus without the inhibitory 

 would give, and that this grade of contraction is fairly quickly reached, and 

 that then this grade continues unaltered provided there is no alteration in 

 the antagonistic stimuli. In other words, the myograph traces under the 

 combined stimulation a plateau (figs. 5 and 6) following on a brief descent. 

 The same plateau is seen when combined excitatory and inhibitory stimulation 

 follows on purely inhibitory stimulation (fig. 7). This plateau indicates that 

 under the combined stimuli a condition of equilibrium is reached, the two 

 opposed reflex influences of excitation and inhibition balancing at a certain 

 level of contraction or relaxation, the length of the muscle then remaining 



Fig. 7. — Reflex contraction of Vastocrureus. The contraction is of two grades in each 

 observation, according as there is concurrent stimulation of inhibitory and excitatory 

 afferent, and of excitatory afferent alone. C denotes time of stimulation of contra- 

 lateral peroneal nerve, I of ipselateral peroneal. Cat, decapitated preparation. Time 

 in seconds. 



constant. This result is such as might be expected. It is a result, however, 

 which in my experience is not obtained when reflex inhibition, however 

 feeble, is pitted against that kind of reflex excitation which the muscle 

 (extensor) expresses as tonus. A tonus preparation of the extensor muscle 

 can be obtained by decerebration produciug decerebrate rigidity. The 

 relaxation caused in such a preparation by reflex inhibition progresses so 

 long as the inhibitory stimulus continues (fig. 8). The weaker the inhibitory 

 stimulus the slower the rate of relaxation, but the relaxing of the muscle 

 progresses, so long as the inhibitory stimulus continues, until the full degree 

 of relaxation and the post-mortem length of the muscle is gradually reached 



