[Descending neuronal projections to the lumbar segment of the spinal cord of cats]

In the experiments, performed on cats by means of retrograde axonal horseradish peroxidase transport, localization of the sources of descending supra- and propriospinal projections to the area of the lumbar parts of the spinal cord, where the generator of locomotor movements is located. After local administration of horseradish peroxidase into the spinal cord, the greatest amount of the labelled neurons is observed in the ipsilateral reticular formation and in the Koelliker-Fuse nucleus. Comparison of the number of neurons, forming the descending projections from the I cervical up to the IV lumbar segments demonstrates an essential predominance of short propriospinal connections over the long, as well as over the supraspinal ones.