Could a portion of the spinal cord be isolated by cutting the pathways of incoming nerve impulses and the animal be kept alive, the following questions might be answered: First, is such functionally isolated nervous tissue capable of surviving and what structural alterations does it undergo ? Second, does the isolated nervous tissue exhibit activity; 5s the spinal cord autochthonous? Third, is the so-called trophic control of non-nervous tissues by the nervous system exercised by physical integrity of the nervous tissue, by virtue of some nutritional relationship, or does it derive from activity nervously initiated. This last question may be answered only if the nervous tissue survives but is inactive.If the anterior spinal roots are entirely efferent, the isolation of a length of spinal cord together with its efferent nerve fibers is possible. Six-week-old puppies, litter mates, were used for the attempt. I n a one-stage operation under ether anaesthesia the lumbar and sacral dorsal roots were cut intradurally on both sides and the cord transected above and below. Autopsy showed that the upper transection fell between the last thoracic and first lumbar se,ments in each case, and the lower transection in the last sacral segment in the first two animals and in the mid-sacral region in the third.
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FOUR PLATES (THIRTY FIGURES)That denervated skeletal muscle atrophies and later degenerates, is a matter of common experience, but the stages of these processes and the ultimate fate of the muscle tissue have never been fully studied. Furthermore, although lesion of the motor neurone is, beyond question, the prime factor in this sequency of atrophy and degeneration, that it is the only factor, is not so certain. The other innervations of the organmuscle-the sympathetic supply to its blood vessels, a rich and varied afferent contribution from posterior roots, even perhaps the much discussed but still problematical posterior root efferent distribution might influence the course of events. according as they were included in the lesion or the left intact. That none of these innervations is by itself responsible far maintaining the integrity of the fiber of skeletal muscle in any part, has previously been demonstrated (Tower, '31 a and b). Continuing with this work, the present study was designed to determine whether or not denervation of the tissucskeletal muscle, by section of ventral roots, is equivalent, qualitatively and quantitatively, to denervation of the organ-skeletal muscle, by section of peripheral nerves. And in the event that a discrepancy developed, provision was made of experiments to identify accessory factors. Before the effects of different lesions could be assayed, however, the present investigation had to remedy the lack of detailed knowledge of the cytology of atrophy and degeneration in muscle, particularly for the 1 THE
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