Co-ordinated Movements after Nerve Crossing, &c. 435 



the impulses intended for the trapezius being directed to the face. If 

 the arm was continued held up, these contractions of the face passed off. 



III. General Conclusions. 



1 . In the fore-limb of the dog, the nerve supply of the flexor muscles 

 may be crossed with that of the extensor muscles, with the result that, 

 despite the altered innervation, the animal regains, as before^ the 

 power of performing voluntary co-ordinated movements of the limb. 



2. The fact of crossing the nerves does not add materially to the 

 time which would be required for recovery of function of the limb if 

 the same nerves were simply divided and reunited by suture as accurately 

 as possible. 



3. The result of crossing the nerve supply of antagonistic groups of 

 muscles is that the nerve centres which formerly innervated the one 

 group now serve for the other group, and this alteration extends to 

 the cerebral cortical centres, which become interchanged in position and 

 retain their irritabilit}'. 



4. The cerebral cortical centres which have been made to interchange 

 their positions by the crossing, are able, in response to the will, to emit 

 impulses which can cull forth in the new peripheral terminations move- 

 ments in perfect co-ordination. 



5. In man the facial nerve may be detached from the facial centre, 

 attached to the spinal accessory nerve, and the facial muscles thus in- 

 nervated by the spinal accessory centre, with the result that co-ordin- 

 ated movements of the face, both voluntary and reflex, are at least in 

 part restored. 



6. In the case of reunion of a divided nerve, it is not necessary to 

 suppose that regeneration restores the old paths for the nervous im- 

 pulses, since, if new paths are formed by the imperfect co-adaptation of 

 the divided nerve ends, with the result of altering the connections 

 between central nerve cells and peripheral endings, the organism has 

 the power of compensating this alteration. 



7. In the case of paralysis of a muscle or group of muscles, if the 

 nerve supplying the affected muscle or muscles is grafted on to a 

 neighbouring efferent nerve supplying muscles which are healthy, it is 

 probable that the affected muscle or group of muscles, if not already 

 destroyed by degenerative process, will regain its normal function. 



2 I 2 



