Proceedings of the Royal Society of London; Biological Sciences Volume 78

Proceedings of the Royal Society of London; Biological Sciences Volume 78

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1906 edition. Excerpt: ...later the passage of impulses finds expression in the marking out of definite fibrillar tracks, some undifferentiated protoplasm remaining as the inter-fibrillar substance. It is pretty clear that the great function of the sheath is as a nutritive organ; its protoplasm is at first laden with yolk, and this is gradually used up as the nerve trunk develops within it. That the main function of nuclei, apart from reproduction, is to control cytoplasmic metabolism is well recognised, and the nuclei of the sheath are able to exercise this control over the active metabolism of the developing nerve trunk, which is destitute of nuclei of its own. Connected with this relation is, no doubt, the active multiplication of these nuclei observed in early stages of nerve regeneration. In such regeneration it may well be that the protoplasmic matrix of the nerve simply repeats the process of its original development, increasing in size and then developing nerve fibrils within itself. On this view the process which takes place in the peripheral segment of a cut nerve would be somewhat as follows: --The fibrils, no longer subject to the stimulus of passing nerve impulses, revert to their protoplasmic condition, and the sheath becomes highly active: it increases in thickness, and its nuclei multiply; its protoplasm digests the remains of the medullary sheath. Supplied with nourishment by the activities of the surrounding sheath, the protoplasm behaves just as it does in ontogenetic development; it grows--probably slowly---a.nd so gaps are bridged over; as soon as it becomes continuous, nerve impulses begin to play backwards and forwards in its substance and cause again a differentiation into fibrils. As part of the impulse tracks persist at the central stumps..show more

Product details

  • Paperback | 174 pages
  • 189 x 246 x 9mm | 322g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 123674246X
  • 9781236742469