416 On Reciprocal Innervation of Antagonistic Muscles. 



be obtained by electrical excitation of the tract in the crura cerel-ri, 

 when, as sometimes happens, that excitation evokes flexion at elbow 

 or at knee. This and the previous fact which evidences that the 

 result is obtainable after complete removal of the whole cerebrum 

 bear out the view arrived at in my former paper that for this 

 reciprocal and, as I believe, elementary co-ordination, it is not essen- 

 tial that " high level " centres (Hughlings Jackson) be employed. 

 I incline to think, however, that this kind of co-ordination at elbow 

 and knee is probably largely made use of in movements initiated via 

 the cerebral hemispheres as well as in the lower reflexes, on the 

 observation of which the present Note is based. This conclusion is 

 indicated by its occurring in response to excitation of the pyramidal 

 fibres in the crura. In the case of the reciprocal in nervation of 

 antagonistic ocular muscles I was able to prove that it took place 

 even in " willed movements." It seems, in view of what has been 

 shown above, legitimate to extend that result to the additional examples 

 afforded by elbow-joint and knee. 



Regarding the innervation of the triceps brachii and quadriceps 

 extensor cruris, it is interesting to note that these muscles, which are 

 of all among the limb muscles particularly difficult to provoke to 

 action by local spinal reflexes, are the very ones which, when the level 

 of the transection is pontial or prepontial, exhibit tonic contraction the 

 most markedly. The well-known and oft-corroborated Sanders-Ezn 

 phenomenon of inaccessibility of the extensors of the knee to spinal 

 reflex action has, as I have recently shown, certain limitations, but 

 at the same time so long as the transection is spinal even when 

 carried out so as to isolate not merely a portion of, but the whole, 

 spinal cord entire from bulb to filurn terminale does apply very 

 strictly to excitations arising in its own local region proper. And 

 the spinal reflex relations of the triceps brachii in this respect, as 

 pointed out elsewhere, somewhat resemble those of the distal portion 

 of the quadriceps extensor of the leg. Alteration of the site of tran- 

 section from infrabulbar to suprabulbar levels works a curious change 

 in this. The Sanders-Ezn phenomenon then becomes subject to strik- 

 ing contravention. I have, after the higher transection, several times 

 seen excitation of the hind foot itself provoke unilateral ideolateral 

 extension of knee, a result incompatible with the Sanders-Ezn rule 

 even under the limitations of ideolaterality, &c., which I consider 

 must be attached to it. And similarly with the triceps at the elbow. 



The difference between the accessibility of the quadriceps to reflex 

 action after infrabulbar and after suprabulbar transection may, how- 

 ever, be less abrupt than it appears at first sight, and a superficial 

 rather than a fundamental distinction. When extensor rigidity has 

 ensued at elbow and knee after suprabulbar transection, the reflex 

 excitability of triceps brachii and quadriceps cruris seems in a man- 



