As has been previously found by other observers, the paralysis which results from section of the pyramid tracts in the medulla oblongata is not complete and persistent. There is therefore some other path by which volitional impulses arising in the cortex reach the motor cells of the cord. 2. Such an alternative path appears to be furnished by the descending fibres of the ventral columns and of the ventral parts of the lateral columns of the cord. Section of these parts produces at least as complete and persistent paralysis in the monkey as does section of the pyramid tracts themselves. 3. This result is not due to the inclusion of the prepyramidal tracts in the section, since it is produced when these are not involved. 4. The question is discussed whether the paralysis produced by section of the ventro‐lateral tracts is due to the severance of an encephalo‐spinal path, or to loss of tone of the neuro‐muscular apparatus of the cord. The conclusion arrived at is, that such loss of tone as might result from the section would be insufficient to produce so complete a block to impulses emanating from the motor cortex as results from the section of these tracts, and that the ventro‐lateral descending fibres therefore constitute an alternative path by which volitional impulses pass from the brain to the ventral horn cells of the cord, although in a less direct manner than by the pyramid tracts themselves. 5. In vertebrata below mammals this probably represents the only path between the higher centres in the brain and the lower motor centres in the cord. 6. There is no evidence of any permanent sensory paralysis resulting from section of the ventral column and ventral part of the lateral column, even although the injury may include the tract of Gowers.
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E. A. Schäfer (1910) studied this question.