On the restoration of co-ordinated movements after nerve-crossing, with interchange of function of the cerebral cortical centres / by Robert Kennedy.
- Kennedy, Robert, -1924.
- Date:
- 1901
Licence: In copyright
Credit: On the restoration of co-ordinated movements after nerve-crossing, with interchange of function of the cerebral cortical centres / by Robert Kennedy. Source: Wellcome Collection.
Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.
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![they did not connect, not only, as Cunningham believes, may voluntary movements in the muscles be possible, but voluntary movements may be carried out in as perfect co-ordination as under the old conditions. Thus the alteration extends to the cerebral cortical centres, and is not, as Stefani believes, limited to lower centres with destruc- tion of the cortical centres. This is proved by the results of cerebral stimulation, which have already been described; for the centre for flexion in Experiments I. and II. was clearly interchanged in position with the centre for extension. The return of vohmtary co-ordinated movements, involving the interchange in function of the cortical centres for flexion and extension, might be ex]3lained as the result of a j)rocess of education, the source from which the brain derives its informa- tion of the new conditions, and of the necessity for an alteration of movements, being, as ScHiFF points out, the aflferent impulses. Schiff takes these afterent impulses to be those which ascend froni tlie radio-cai'pal joint and skin of the fore-arm, wliich are supplied by nerves which have not l)een included in the crossing, and he disregards the muscular sense. But the afferent impulses which are of educational value are probably conveyed along the crossed nerves after functional union has been effected. It is difficult to estimate in dogs tlje exact date of recovery of sensation, as the animals will only indicate restoration of sensation when recovery is advanced suffi- ciently far that pain can l)e })roduced by stimuli ap2:)lied to the skin. Thus, for a considerable time after restoration of sensation, the animals will, unless of irritable temper, allow needles to be thrust into the limb without making any sign, for the simple reason that such, although producing sensation, do not produce pain. It may, however, be taken from analogy with the condition in man that sensation is restored earlier than motion ; for with the restoration of conductivity of the nerve, sensation returns. In the case of mf)tion, however, the muscles rapidly undergo some degenera- tion as the result of the temporary deprivation of the influence of the nervous system, and only begin to recover on restoration of conductivity of tlie nerve, and after this event some time must elapse before they are cap.djle of responding to normal stimuli. On recovery of the muscles the earlier restored sensation might lead to a voluntary alteration of the function of the centi'es in the following way :—When the animal allows the paw to touch the ground for tlie first time after restoration, contact on the palmar sin^face is felt as contact on the dorsum. The animal thus feels that the dorsal surface is directed downwards, and to correct this tries to make the movement which before the crossing produced extension. This effort at movement, however, now produces flexion, and the result is that placing its weight on the ground with the dorsal surface of the paw directed downwards, and finding no support in this position, it falls on tlie lower end of the radius. It therefore is informed that something is wrong, and learns by repeated experiences that, in order to attain a rigid position of the foot with the palmar surface down, the opposite movement of what was formerly flexion has to be made. When this is established, then what was formerly dorsal](https://iiif.wellcomecollection.org/image/b21456513_0029.jp2/full/800%2C/0/default.jpg)
