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

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.

15/46 (page 137)

$like Stefani, to have found restoration of co-ordinated movements. This result lie explains as due to tlie volitional correction by the animal of movements which sensa- tion informs it no longer result from the same impulses as before the exjjeriment. He still, however, maintains the impossil)ility of an alteration of function after crossing nerves like the vagus and hypoglossal. This difference between nerves of voluntary and tliose of involuntary function, however, according to IIawa does Jiot obtain. 'Jims the latter may have their co-ordinated functions restored through the former, and vice lu rsd, and tliis view is Confirmed by Lanc4LEY, who finds tliat stinudi for nramal sympathetic functions can 1)6 started in the vagus centre and conducted through the vagus nerve. The mode of carrying out tlie experiments has also influenced the results. Thus, in order to prevent confluent reunion, IIawa, Schiff, and Langley crossed «>nly one ]ieripheral and one central end, widely excising the other two ends. In Schiff's and Langley's and certain of IIawa's experiments, this method did not vitiate the results, as the two nerves were distributed to entirely difl'erent structures ; but in Rawa's experiments on the nerves of the extremities this method, as stated al)ove, was not compatible witli perfect recovery of the limb, as therel)y either the flexor or the extensor muscles only were innervated, the opposing group l)eing left unsup})lied, a condition necessarily resulting in contracture, wliich must have made the interpre- tation of the results extremely dubious. Cunningham, howe\'er, made a double crossing, and prevented confluent reunion by stitching round each seat of union a layer of fascia, wdiile Stefani made double crossings in all his experiments exce})t one, but except in the latter, seems not to have taken precautions to prevent confluent reunion other than the distance which se])arated the two points of union. That tliis was ]iot a safe })i'ocedure is shown from tlie fact that one of his experiments had to be rejected on account of confluent reunion. Stefani's experiments were not followed by a })erfect use of the limb liy the animal, permanent flexion developing in all in whicli tlie crossing had been eftective. This is to be explained by the fact that he crossed in them the musculo-spiral with the median only, leaving the \dnar nerve intact. A method of this kind leaves one nerve to sup})ly the flexors as before, while the whole supply of the extensors has to be carried on through the crossed nerve. The balance of op|)osing action of the two groups is thus disturbed, and the flexors are more thari likely in the course of the experiment to exhibit a preponderance of action. The conditions were rightly arranged in Cunningham's experiments, in which both median and ulnar were crossed witli the musculo-spiral; but he, of course, did not find return of co-ordinated motion. VOL. CXOIY. B. T$