イヌの脊髄神経根およびその分枝に関する研究(<特集>脳と神経の研究)

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タイトル別名
  • イヌの脊髄神経根およびその分枝に関する研究
  • イヌ ノ セキズイ シンケイ コン オヨビ ソノ ブンシ ニ カンスル ケンキュウ
  • STUDIES ON THE RADICES AND KAMI OF THE SPINAL NERVES IN DOGS
  • 原著
  • Original Article

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The ventral and dorsal roots, ventral and dorsal rami and their communicating rami in the left side of the upper thoracic (T_3), lower thoracic (T_9) and lumbar (L_1; L_3, L_5) spinal nerves were studied with Fukuyama's method (fan-wise split preparation) in forty-six adult dogs. These nerves were examined macroscopically and histologically, then nerve degeneration experiments conducted to investigate the course and distribution of the myelinated fibers constituting the nerve. The results obtained are summarized as follows : 1. The myelinated nerve fiber constitution of the ventral roots was as follows: The maximum sized fibers occupied 37.2% ; the large sized 3.9% ; the medium sized 12.3% and the small sized 46.7% on an average. The L_5 ventral root however was characterized by the lowest value (8.9%), of the small sized. 2. The myelinated nerve fibers of the dorsal roots commprised 30.1% of small sized, 11.6% of large sized, and 45.0% of maximum sized fibers on an average. The small sized 13.3% of medium sized, fibers of the dorsal roots were less than those of the ventral roots. 3. The ventral rami resembled the dorsal rami in the fiber constitution without reference to height of the segments. 4. Ratio of the frequency of the dorsal root-fibers to that of the ventral root-fibers in the ventral rami stood at 65.3%-34.7%, while in the dorsal rami, the ratio was 72.3%27.7%. In the ventral and dorsal rami, the dorsal root-fibers were more numerous than the ventral root-fibers. 5. The sympathetic myelinated preganglionic fibers via the ventral root were mostly small sized, with only a part perhaps medium sized. 6. The somatomotor fibers via the ventral root contained the most numerous maximum sized fibers and they decreased in number in proportion to the size of the fiber. 7. The sensory fibers via the dorsal root were of all sizes (small to maximum), in which a majority of maximum and large sized fibers innervate perhaps the skin and striated muscles; the medium and small sized fibers chiefly the viscera.

8. The fiber constitution of the white communicating rami were uniform through T_3, T_9, L_1; L_3: The small sized fibers occupied 92.5%; the medium sized 5.2%; large sized 1.7% and maximum sized fibers 0.8%. The small fibers were very numerous and ratio of the frequency of the ventral root-fibers to that of the dorsal root-fibers in the white rami stood at 55.0%-45.0%. 9. The grey communicating rami of the L_1, L_3, L_5 contained also the myelinated fibers beside the unmyelinated fibers, but the former varied in size, a majority of which were the dorsal root-fibers. 10. With wallerian degeneration method, no myelinated afferent fibers could be found in the ventral roots. The small sized dorsal root-fibers were considered to be conducting visceral sensation. 11. No myelinated efferent fibers could be found in the dorsal roots in the eary periods (7 days) after section, however, at later periods (40 & 50 days) after section, there occurred numerous very small myelinated fibers in the central ends of divided dorsal roots. These fibers are the regenerating, not true, efferent dorsal root-fibers. While, on the dorsal roots, a few aberrant nerve cells were found, which had the nerve fibers running toward the periphery.

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