ネコ後根線維の脊椎および延髄への投射について 第3報
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概要
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The projection of thoracic dorsal root 1 to 13, to the spinal cord and the Medulla oblongata were investigated. For this purpose, each dorsal root of 15cats was cut singly, and degeneration fibers were traced by Nauta-Gygax or Ebbesson-Heimer technique. The results are as follows. (A) Pathway (a) Entrance level The dorsal root fibers enter the Lamina I through mainly the Fasciculus posterior and sparsely the Fasciculus dorsolateralis. The fibers through the Fasciculus posterior run ventrally the inner part of the Lamina II, III&IV, and form the dorsolateral fiber plexus in the central part of the Lamina V to VII. The fibers of lateral half passing through the plexus run toward the Lamina VIII&IX. The fibers of medial half passing through the plexus run to the ventrolateral part of the central canal and form the ventromedial fiber plexus. Fibers passing through this plexus, run toward the Lamina VIII&IX. (β) Rostro-caudal extention of the dorsal root fibers in the spinal cord excepting the entrance level (1) In the Fasciculus dorsolateralis, dorsal root fibers ascend and descend 1 segment. In the Fasciculus posterior, besides the fibers running to the Medulla oblongta, there are the fibers enterring the gray matter 1 segment up and down, and descending 3 to 6 segments. (2) In the gray matter, the dorsolateral fiber plexus and the ventromedial fiber plexus ascend 3 to 8 and 2 to 8 segments, respectively and descend 4 to 7 and 1 to 3 segments, respectively. (3) In the Medulla oblongata, root fibers ascend through the white matter surrounded by the Nucleus gracilis and the Nucleus cuneatus. (B) Projection sites (1) In the spinal cord, The Nucleus posteromarginalis in the first to the thirteenth segment receives 3 dorsal roots via Fasciculup dorsolateralis and Fasciculus posterior. The Nucleus proprius of the posterior horn in the first to the thirteenth segment receives 5 to 8 dorsal roots, the Nucleus thoracicus in the secound to the thirteenth segment 10 to 14 dorsal roots and the moter cells of the antrrior horn in the first to the thirteenth segment 4 to 7 dorsal roots. (2) In the Medulla oblongata, the Nucleus gracilis, the Nucleus cuneatus and the Nucleus cuneatus lateralis receive mainly and the Nucleus X and Nucleus Z of Brodal receive sparsely the dorsal root fibers. The localization of projection fibers in the Nucleus thoracicus, the Nucleus gracilis, the Nucleus cuneatus and the Nucleus cneatus lateralis are recognized.