. A manual of diseases of the nervous system. itial neuritis, or the fibres themselves in the paren-chymatous form. Isolated neuritis is generally adventitial, andwiQ be first described. In acuteinflammation the affected part ofthe nerve is red, softened, andswollen. The redness dependson distended vessels, which maybe visible on the surface; inmore acute cases it may resultfrom the presence of minutehaemorrhages. The swelling isdue to oedema, or to a sero-fibrinous exudation, sometimesjelly-like in aspect. The micro-scope shows leucocyte-like cor-puscles surrounding the vessels,infiltrating t
. A manual of diseases of the nervous system. itial neuritis, or the fibres themselves in the paren-chymatous form. Isolated neuritis is generally adventitial, andwiQ be first described. In acuteinflammation the affected part ofthe nerve is red, softened, andswollen. The redness dependson distended vessels, which maybe visible on the surface; inmore acute cases it may resultfrom the presence of minutehaemorrhages. The swelling isdue to oedema, or to a sero-fibrinous exudation, sometimesjelly-like in aspect. The micro-scope shows leucocyte-like cor-puscles surrounding the vessels,infiltrating the sheath (Fig. 44)and acc»iiulating between it andthe nerve. There may be evenemail extravasations of is extremely rare. These changes may be limited to thesheath in what is called perineuritis, or may extend into thesubstance of the nerve in interstitial neuritis. In the latter casethe lymphoid corpuscles infiltrate the septa, and may even be seen inthe substance of the f ascicidi, between the nerve-fibres. These changes. Fig. 44.—Neuritis: degeneration of nerve-fibres, the myelin broken up into masses,globules, and granules. Accumulation ofleucocytes in uerve-sheath. Proin a caseof multiple neuritis. (After Ley den.) 84 NEURITIS. may be continuous along a considerable tract of tbe nerve (diffuseneuritis), but more frequently they are chiefly marked at certainplaces, which are separated by portions of the nerve which are solittle affected as to appear to the naked eye to be normal (focalor disseminated neuritis). The foci of inflammation are chieflysituated at places where the nerve turns round a bone, or emergesfrom 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 fibroustissue, within which the sheath cannot expand; its swelling then exertspressure on the fibres. When the inflammation
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