Synopsis of lectures upon diseases of the nervous system / by M. Allen Starr.

  • Starr, M. Allen (Moses Allen), 1854-1932.
Date:
1894, ©1893
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Licence: Public Domain Mark

Credit: Synopsis of lectures upon diseases of the nervous system / by M. Allen Starr. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    THE PERIPHERAL NERVES AND THEIR DISEASES. Structure of the nerves. Bundles of nerve fibres—large or small. Structure of a nerve fibre : i. Axis cylinder, a long process of some nerve cell. 2. Medullary sheath of myelin—a fatty in- sulator, interrupted at the nodes of Ranvier. 3. Connective tissue sheath of Schwann, with its nucleus. Nerve fibres are bound into bundles by connective tissue ; endoneurium, peri- neurium. The visceral nerve fibres have no medullary sheath. All nerve fibres branch during their course in the central nervous system, sending out collaterals, but do not branch in their peripheral course. They arise from a nerve cell. They terminate in fine brush-like expansions which are spread out in the skin, or on a muscle, or around another nerve cell. Nerves are divided into motor nerves and sensory nerves, ac- cording to the mechanism to which they are attached. Motor nerves convey impulses outward, sensory inward. Motor nerves grow outward from large nerve cells in the spinal cord. Sen- sory nerves grow from cells in the posterior spinal ganglia, which send one branch to the surface, and the other into the spinal cord. Neuritis. Neuritis may occur in a single nerve, or in a plexus. Causes.—Injuries, strains, pressure, compression in fractures, rheumatism, gout, cold. Pathology.—i. Parenchymatous neuritis, congestion and exu- dation in nerve trunk ; swelling and degeneration of individual fibres ; i, axis cylinder broken and disintegrated in fatty mass ; 2, medullary substance separated into segments and fatty globules, and mingled with granules and nucleated cells ; 3, connective tissue sheath shrunken and empty. Nuclei multiply. Products of degeneration liquefy and are absorbed.