224 



Prof. C. S. Sherrington. Reciprocal [Nov. 13, 



femoris muscles, hip-flexors, the effect of stimulation of the central end of the 

 peroneal nerve is contraction of the ipsilateral muscle and inhibitory 

 relaxation of the contralateral (fig. 4). So also with psoas, and sartorius 

 (fig. 5), and semitendinosus, the latter a flexor of knee. Yet with these 

 flexors, although thus reciprocally innervated, it has been shown that, under 

 certain circumstances, they exhibit identical reflex innervation, for instance 

 when nociceptive stimulation is applied concurrently to both feet.* And 



.L.ken-sor 

 fa ac fen, 



I , pprrjri - 



Fig. 4. 



Fig. 4. — Flexor muscles, tensor jascice femoris, of right and left hips. Stimulation of right 

 peroneal nerve, and then of left peroneal nerve. Decerebrate cat. 



Fig. 5. — Flexor muscles, psoas and sartorius, of right and left hips. Stimulation of right 

 peroneal causes contraction of the right muscles and inhibitory relaxation of the 

 left. Stimulation of the left peroneal causes inhibitory relaxation of the right 

 muscles and contraction of the left. Decerebrate cat. 



when the two peroneal nerves right and left are concurrently stimulated with 

 faradisation of approximately equal intensity, the two flexor muscles right 

 and left both contract together (fig. 6) and exhibit fully identical reflex 

 innervation. Here, however, the identical innervation presents itself in the 

 form of concurrent contraction not of concurrent relaxation as was the case 

 with the extensors. With the flexors, therefore, the excitatory effect of each 



* Sherrington, in ' Schafer's Handbook of Physiol.,' 1900, vol. 2, p. 840 ; ' Integrative 

 Action of Nervous System,' p. 225, 1906. 



