DELAYED UNION. — When the ends are not in apposition the pathological changes depend to a degree upon the distance between them. Even here, if the ends are not too far apart, reunion with true regeneration of the nerve structure often occurs, the axis-cylinder and the myelin being regenerated to a more or less perfect degree. Repair may take place when the ends are an inch apart, and, doubtless, as shown by a few reported cases, even when a much greater distance exists. Schiff, for instance, wit nessed complete restoration of conductiv ity after a piece two inches long had been exsected from the vagus of a (log. Still, such a result should not be taken as a guide in practice.
Fifty-five eases of section of nerves seen, some sutured and some not, and the notes examined of over two hundred and fifty eases of sectioned nerves with in, re or It ss complete recovery. The of primary union is denied. he ease, reported as instanees of pri union believed to have been cases w here stir,ation alone. and not motion, hall 14.111 the return of sensa tion ha% ing depended upon anastomosis, and not upon leunion of the eut nerve. In favoiable cases motion mill be found to return as soon after secondary as after primary suture. The degeneration which follows every section necessarily occupies many weeks, and these may pass without the nerve bein,g united. J. K.. Mitchell (Jour. Nerv. and Alental Dis., June, '95).
After suture of nerves early return of sensation must be regarded as indicating a restored conductivity of the divided nerve. The imperfect or non-return of motion must be taken to imply atrophy or destruction of the muscles. Micro scopical examinations reported. Both central and peripheral portions of un united nerves contain bundles of young nerve-fibres, to the sides of which spindle-shaped nuclei are attached at fre quent intervals. Where the nerve-ends were united by a eieatrieial segment without conductivity being restored, the segment m as found to consist of a dense net-work of connective tissue con taining bundles of young nerve-fibres in its meshes. Portions excised from the central ends of the nerves showed no trace of old myelin-fibres or of degener ated fibres, but AN ere made up of bundles of young nerve-fibres, which could be seen taking origin within the old sheaths of Schwann. No evidence was found of Krause's ascending degeneration, the old axis-cylinder and myelin-sheath being destroyed in the peripheral segment in the ultimate portion of the central seg ment.
Young nerve-fibres are developed in the peripheral segment as well as in the end of the central segment, even ,,vhile there is no connection between the two. These young nerve-fibres arise within the old sheath of Schwann from the pro toplasm and nucleus of the interannular segments. The spindle cells formed from the protoplasm and nuclei of the inter annular segments elongate and unite to form protoplasmic threads \I ith the elongated nuclei attached to their sides. The central portion of the protoplasmic thread develops into the axis-cylinder, while myelin is deposited in drops in the outer portions, the protoplasm of which remains with the nucleus as the neuro blast of the new intcrannular segment. As long as the conductivity of the nerve is not re-cstablislied the development of the fibres proceeds only to a certain stage, and, as the new fibres three and eighteen months after division present the same characters, this stage may be regarded as a resting stage, depending, for its further development, on re-estab lishment of function. The cicatricial in terealary segments of a spontaneously reunited nerve may be permeated from end to end by young fibres without re establishment of function if the amount of cicatricial tissue present in the mass is sufficient by its pressure to prevent the passage of impulses. Robert Ken nedy (Report to the Royal Soc., Feb. 11, '97).
Prognosis.—While sensation and mo tion are about equally affected imme diately after the injury, sensation is usu ally the first to return. The improvement is generally rapid when suitable condi tions of repair prevail. The chances of complete recovery, however, greatly de pend upon the nature of the injury and the time elapsed between the accident and the time the remedial measures are instituted. When the muscles are not completely degenerated, much can be done with persevering treatment— months and even years being sometimes required to bring about a satisfactory result. The rapidity with which degen eration begins in the nerves and the early involvement of the muscles render it imperative, therefore, that in all cases of nerve-injury active measures should be resorted to at once.