The distribution of motoneurons innervating hindlimb muscles in the terrapin Pseudemys scripta elegans

The distribution of motoneurons innervating a number of hindlimb muscles in the spinal cord of the terrapin Pseudemys scripta elegans was studied by means of intramuscularly injected horseradish peroxidase (HRP). It appeared that motoneurons innervating knee extensors were localized more rostrally in the spinal cord than those innervating knee flexors and hip retractors. Muscles on the dorsal side of the limb were positioned more ventrally in the ventral horn compared to motoneurons innervating ventral muscles. Thus, an evident somatotropic organization of motoneurons was demonstrated in the chelonian spinal cord.