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Prof. C. S. Sherrington. Nervous Rhythm [Feb. 3, 



that the antagonist stimuli must not be very unequal in intensity if they are 

 to provoke the rhythmic reflex (fig. 9 shows this with flexor muscles), but 

 that on the other hand the stimuli may yet succeed in producing the rhythmic 

 reflex when quite indubitably and markedly unequal in intensity, if that 

 inequality does not go beyond certain limits. 



Fig. 10 will serve as illustration. In this experiment the thresholds of r. 

 and 1. nerves lay at 195 and 20 - 5 respectively. The physical circuits were 

 hardly appreciably unequal, for the thresholds changed only to 19 - 2 and 

 20 - 8 when the coils were interchanged for the two nerves by the double 



Fig. 11. — A series of reflexes, phasic and tonic, provoked in the isolated right and left 

 vastocrureus muscles by short non-concurrent faradisations of right and left peroneal 

 nerves. The numerals mark some salient corresponding events in the signal lines 

 and myograms. The inhibitory relaxations produced in right vastocrureus, ft.V., by 

 stimulation of r.p. are followed by rebound contractions ; similarly the inhibitions of 

 L.V. are followed by post-inhibitory rebounds on withdrawal of each stimulation of 

 l.p,, left peroneal. Besides the reciprocal reflex movements induced by each stimulus, 

 the stimuli cause assumption of reflex postures, e.g. under stimulation of r.p. the two 

 myogram lines approach each other, i.e. r. muscle is relaxed (indicating that flexion 

 of right leg would be going on, were the muscles not paralysed) and 1. muscle is 

 contracted (indicating that left limb would be extended). Under stimulation of 

 l.p. the two myograph levers diverge, indicating that left limb assumes posture of 

 flexion and right limb that of extension. This figure gives the separate effects 

 of the two stimuli which, when concurrent, give the stepping reflex recorded 

 in fig. ] . Decerebrate cat. Time in fifths of seconds. 



