ISOLATION OF INTRINSIC AND MOTOR MECHANISM OF THE MONKEY'S SPINAL CORD

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Abstract
The intrinsic mechanism of the spinal cord is compounded of all nerve fibers which both originate and terminate within the cord, and of their cells of origin. Using 3 monkeys (Macaca mulatta), a portion of this intrinsic mechanism together with its associated final motor mechanism was isolated from the remainder of the nervous system by transecting the spinal cord at two levels, one thoracic, the other sacral, and severing all posterior roots between. On the day following, the right sciatic nerve was also cut. For 2 wks. the monkeys were studied, after which they were killed and autopsied. In 2 of the animals the isolated region of cord was found in good condition, and specimens were prepared for histological study by both Nissl and reduced Ag technique. In the 3d animal, the isolated region was necrotic. Altogether, this study demonstrates the feasibility of isolating regions of mature spinal cord from all ingoing nerve impulses and utilizing them for examination of various questions in neuro-anatomy and neurophysiology. It has given a picture of the intrinsic and motor mechanism of the spinal cord cleared of posterior root and descending fibers, showing the magnitude, variety and arrangement of the intrinsic system in the monkey. Finally, it has confirmed the conclusion previously reached after very much longer study of isolated segments in dogs, that the mammalian cord mechanism operates only under the stimulus of arriving nerve impulses. Deprived of such excitation the spinal cord produces no activity which reaches effectiveness in skeletal musculature.

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