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
Catalogue details

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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    certain whether the stimulation of a particular centre evoked contractions only in the extensors or only in the flexors, these muscles were exposed after the examination of the seat of crossing had been made, and the surface of the brain again stimulated. It was possible, although the movement of the paw produced by stimulation of a centre was flexion or extension, that the stimulation might at the same time cause some contractions in the opposing set of muscles, contractions too weak to resist the opposite movement. As the result of these examinations it was found that in Experiment I. the centres controlling flexion and extension of the fore-limb which had been operated on, had interchanged their positions. The extension centre was quite distinct and ]yare, and situated in the position occupied normally l^y the flexion centre, while farther out and further forwards in the normal position of the extension centre was situated the only point, stimulation of which caused contraction of the flexor muscles of the paw. This centre was not, however, pure, as conti'actions of the flexors were almost always accompanied by stronger contracti(jns in the extensor muscles. Compared with tliis condition, the opposite side of the Ijrain showed the centres of the fore-limb to be well defined and situated normally. In Experiment II. the result of the examination v/as even more distinct; frr in this case the affected gyrus shov/ed the centres for flexion and extension perfectly well defined and pure, but v/ith their positions interchanged. The opposite gyrus also showed the two centres situated normally and well defined. In Experiment III., in which the neives were not crossed, cerebral stimulation showed the flexion and extension centres situated in their normal positions, being similarly situated on the two opj)osite gyri; but in this case neither on the one nor on the other side were the two centres very well defined, as there was always a certain amount of contraction in the flexors when the extension centre was stijnulated, and vice versa. As regards the degree of irritability of the two sides of the brain in the experiments in which the nerves had been crossed, there was no diminution of irritability of the affected side exhibited, but rather the reverse. Thus, contractions of the muscles of the affected limlj in both cases were evoked by an interrupted current too weak to produce contractions when applied to tlie normal side, and currents suflicie]itly strong to call forth movements when applied to the iiornral side were able to produce a more vigorous movement on the affected side. The condition of the cerebral centres shown in these experiments agrees with that which was found by Cunningham in his experiments, ljut is different from that which Stefani describes ; as the only case in which Stefani found irritability of the affected side of the brain was a case in which the crossing had not remained efficient, and in which, therefore, the muscles continued presumably t(_) receive supply from their old sources, and in all his cases in ^vhich the crossing remained eflicient, the irrita'bility of the cerebral centres disappeared.