. A manual of diseases of the nervous system. al nature, in consequence of which it stains more readilythan in health. Fibres are thus changed adjacent to any increasein the interstitial tissue, and they contrast with the unstained healthyfibres in the vicinity (Fig. 97, c). With or without this change inthe myelin, there is an irregular swelling of the axis-cylinders, suchas is seen on examination in the fresh state. If the fibres are dividedtransversely at the places where the axis-cylinder is swollen, thisappears much larger than normal (Fig. 93, b). Examples of thiswill be found in most of
. A manual of diseases of the nervous system. al nature, in consequence of which it stains more readilythan in health. Fibres are thus changed adjacent to any increasein the interstitial tissue, and they contrast with the unstained healthyfibres in the vicinity (Fig. 97, c). With or without this change inthe myelin, there is an irregular swelling of the axis-cylinders, suchas is seen on examination in the fresh state. If the fibres are dividedtransversely at the places where the axis-cylinder is swollen, thisappears much larger than normal (Fig. 93, b). Examples of thiswill be found in most of the figures. These intense degenerativechanges cause the breaking up of the myelin, and may involve thedestruction of the fibre, the space occupied by it being left empty. * The significance of this vacuolation has been much discussed. It is probablethat the vacuoles form after death, perhaps during the process of hardening, butthat they do not form unless the cells have been altered by disease. They have thussome pathological significanqe,. Fig. 96.—Subacute disseminated myelitis ;part of the posterior column. Nerve-fibresseparated by granular material and productsof degeneration, and by numerous largespider cells. The myelitis in this case wasattended by optic neuritis. (Prom a sec-tion lent by Dr. Dreschfeld.) 308 SPINAL CORD. In other cases, however, the axis-cylinder persists and remains sur-rounded by a narrow zone of myelin. Often a large number of suchshrunken fibres may be found in a part which at first sight appeareddevoid of fibres. This shrinking of the fibres occurs not only as theresult of pressure on them by the connective-tissue elements, but alsowhere there is little interstitial change and no compression.
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