Abstract
It has been shown (Marshall 1 ) that a lesion of the pyramidal tracts in the medulla produces on the whole a less severe disorder of motility than does removal of the motor cortex. Evidence has also been presented which would suggest that lesions of the rubrospinal tracts interfere with 2 groups of reflexes, the “Berührungs-reflexe” of Munk and the contact placing reactions of Rademaker, which are dependent upon the integrity of the motor cortex. The conclusions were drawn that the pyramidal tracts do not form the only significant pathways of discharge from the motor cortex, and that other “extrapyramidal” tracts, particularly the rubro-spinal, participate as well.
If these conclusions are correct, then the removal of the motor cortex subsequent to a section of the pyramidal tracts should produce a paralysis, the severity of which might be more or less proportional to the functional importance of the extrapyramidal pathways descending from the motor area. The present experiments attempt to determine this. In 2 cats the left pyramid was sectioned, and 10 months was allowed for the degeneration of the pyramidal system and its cells of origin in the cerebral cortex. The motor area for the limb muscles (area 4 of Brodmann) which includes the entire post-cruciate gyrus and the lateral half of the pre-cruciate gyrus was then removed on the left side. On the 16th and 17th day the animals were sacrificed and the brain and spinal cord removed. The gross preparations showed the lesions to be as described. Marchi and Pal-Weigert studies are in progress.
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