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



nerves there is, however, another factor controlling the balance of reflex 

 result on the antagonistic muscles. It was shown previously that the 

 ipselateral reflex on the knee muscles is, as compared with the crossed reflex, 

 the prepotent one. Eemembering that the influence of the ipselateral 

 afferent is excitation of the flexor and inhibition of the extensor, while that 

 of the contralateral afferent is inhibition of the flexor and excitation of the 

 extensor, it has been shown that each of these afferent nerves can be made 

 to preponderate in reflex result over the other. This preponderance in effect 

 of the one over the other can be impressed on either the one or the other of 

 the two by simply stressing the intensity of the stimulus to the one it is desired 

 should preponderate. But it is less easy to secure prepotency for the 

 contralateral nerve than for the ipselateral. The ipselateral reflex seems to- 

 function with an inherent greater intensity than the contralateral. Fig. 11 



Fig. 11. — Double-myograph Observation. E marks vastocrureus, F semitendinosus ? . 

 C contralateral stimulus, I ipselateral stimulus. Cat, decerebrate preparation. Time 

 in seconds. Description in text. The myograph lever attached to vastocrureus 

 writes not directly above that attached to semitendinosus, but about a half centimetre 

 to right of it ; arcs cut by the levers on the recording surface when stationary mark 

 the moment of application of stimulus on each myograph line. 



exemplifies the effect that this has on the experimental adjustment of the 

 stimuli required for algebraic summation of excitation and inhibition. The 

 observation opens with stimulation of the contralateral afferent which 

 produces contraction of the extensor muscle and no obvious effect on the 

 flexor, the preparation not being a tonus preparation as regards the flexor.. 

 Two seconds later there ensues stimulation of the ipselateral afferent, 

 stimulation of the contralateral continuing unaltered ; the flexor at once 

 contracts, and the contracting extensor is at once relaxed, and so speedily 

 and fully that its lever gives a vibratory shake after the fall. A second and 

 a half later the ipselateral stimulus is withdrawn ; the contraction of the 

 flexor then dies off, and the contraction of extensor reappears and regains its . 



