Student Theses and Dissertations

Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Techniques were developed for maintaining a bullfrog spinal cord in situ and for recording intracellularly from lumbar motoneurons in this preparation. Fibers in the contralateral and ipsilateral lateral funiculi of the spinal cord which originate at or above the calamus scriptorius were found to produce EPSPs in flexor and extensor motoneurons innervating the hindlimb. These EPSPs appeared to be generated monosynaptically on the somas and proximal dendrites of the motoneurons. Chromatolysis was used to map the location of motoneurons· innervating hindlimb muscles in the bullfrog, Rana catesbiana. These motoneurons were located in the dorsolateral cell column of the ventral horn, but not in the ventromedial column. A somatotopic organization was found, with motoneurons innervating proximal muscles located ventrally and rostrally to those innervating distal muscles. A functional organization was found, in which motoneurons controlling the flexor muscles around any joint were located rostrally to those controlling the extensors. Electrophysiological mapping gave results consistent with this arrangement.


A thesis submitted to the Faculty of The Rockefeller University in partial fulfillment of the requirements for the degree of Doctor of Philosophy

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