A manual of diseases of the nervous system . elves in the paren-chymatous form. Isolated neuritis is generally adventitial, andwill be first described. In acute inflammation the affected partof the nerve is red and swollen. The redness depends on distendedvessels, which may be visible on the surface. The swelling is due tooedema, or to a sero-fibrinousexudation, sometimes jelly-likein aspect. The microscope showsleucocyte-like corpuscles sur-rounding the vessels, infiltratingthe sheath (Fig. 44) and ac-cumulating between it and thenerve. There may be even smallextravasations of blood. Thesecha
A manual of diseases of the nervous system . elves in the paren-chymatous form. Isolated neuritis is generally adventitial, andwill be first described. In acute inflammation the affected partof the nerve is red and swollen. The redness depends on distendedvessels, which may be visible on the surface. The swelling is due tooedema, or to a sero-fibrinousexudation, sometimes jelly-likein aspect. The microscope showsleucocyte-like corpuscles sur-rounding the vessels, infiltratingthe sheath (Fig. 44) and ac-cumulating between it and thenerve. There may be even smallextravasations of blood. Thesechanges may be limited to thesheath in what is called peri-neuritis, or may extend intothe substance of the nerve in interstitial neuritis. In thelatter case the lymphoid cor-puscles infiltrate the septa, andmay even be seen in the sub-stance of the fasciculi, betweenthe nerve-fibres. These changessiderable tract of the nerve (diffuse neuritis), but more frequentlythey are chiefly marked at certain places, which are separated by por- VOL, I. 5. Fig. 44.—Xeuritis : deareneration of nerve-fihrea, the myelin broken np into mnsses,globules, and granules. Accumulation ofleucocytes in nerve-sheath. From a caseof multiple neuritis. (After Leyden.) may be continuous along a con- 66 NEURITIS. tions of the nerve which are so little affected as to appear to the nakedeye to be normal ( focal or disseminated neuritis ). The foci ofinflaninaation are chiefly situated at places where the nerve turns rounda bone, or emerges from canals or fasciae, or divides. The extent to which the nerve-fibres suffer varies much. Theyusually present little change when the inflammation is limited tothe sheath, unless the nerve lies in a bony canal, or in rigid fibr. lustissuf, within which the sheath cannot expand; its swelling then exertspressure oa the fibres. When the inflammation is interstitial thefibres suffer more readily, although not invariably. On the otherhand, they are sometimes found much altered,
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