201 



On Reflex Inhibition of the Knee Flexor. 

 By C. S. Sherrington, F.K.S., and. S. C. M. Sowton. 



(Received and read June 29, 1911.) 

 (From the Physiological Laboratory, University of Liverpool.) 



1. Introduction. 



Study of reflex inhibition has been prosecuted more with extensor centres 

 than with flexor. In the case of these latter, the experimental examination 

 of the inhibition is of necessity somewhat differently circumstanced than in 

 the case of the extensors. For both there is requisite a suitable background 

 of reflex excitement against which inhibition may be evident. With the- 

 extensors this reflex background of excitement can be provided by postural 

 tonus, and such tonus is readily obtained by use of the decerebrate- 

 preparation. With the flexors there is at present no procedure available for 

 providing such tonic preparations. Eecourse has to be taken to the 

 production of reflex excitation of the centres by artificial stimuli applied to. 

 some appropriate afferent channel.* The background of contraction of the 

 flexor muscle against which inhibition can become apparent is thus obtained 1 

 by more artificial means. This latter procedure has its drawbacks; the- 

 background of reflex excitement it provides is less mild and less enduring 

 than that furnished by natural tonus, and it is less enduring exactly in those 

 approximately milder degrees which are particularly favourable for the 

 manifestation of inhibition. On the other hand there are compensations, one 

 being the more complete and rapid variation of the background in regard to-, 

 its medium and higher intensities. 



2. Method Employed. 



As muscles typical of the flexor class we have chosen for our observations semitejidinosus 

 and sartorins (cat). These have been shownt to engage regularly as flexors, of knee and 

 hip respectively, in the nociceptive flexion reflex of the limb, in the reflex step in its 

 flexion phase, and in the scratch-reflex. Each of these muscles is readily prepared for 

 the myograph by detachment of the lower tendinous insertion and liberation of the whole 

 distal half of the muscle, the nerve and blood supply which enter above remaining intact. 

 To immobilise the preparation the procedure has been as follows:— (1) Nerves severed: 

 peroneal, popliteal, small sciatic, femoralis, obturator, external cutaneous and hamstring 

 nerves of both limbs, with the exception in the case of the semitendinosus preparation of 

 the branch to that muscle from the hamstring nerve of one limb, and in the case of the 



* Sherrington, 'Eoy. Soc. Proc.,' 1909, B, vol. 81, p. 251. 

 t Sherrington, ' Journ. Physiol.,' 1910, vol. .40, p. 28. 



