ynyjobi yaqopolo
|
 |   Related post: matter. In proportion as the atrophy of the nerve-elements advances, the fibrillary tissue is developed, and gradually assumes the characters of genuine connective tissue. Re- gressive transformations now take place, fatty granulations are deposited in the interstices of the tubes, and amyloid corpuscles are produced at the expense of the small uninu- clear cells of the intercellular viscous liquid. The absorption of this liquid, favored by the contraction of the connective elements, marks the last stage of the j)rocessus. The diseased tissue, deprived of its juice, is composed solely of connective fibres immediately contiguous, whose unequal shrinkage gives rise to partial distortions. Finally the whole mass becomes of a grayish fawn-color, often closely resembling the tint of ground glass. Charcot has described these histological clianges in the several stages ot" the processus more fully. On placing under the microscope a prop- erly-prepared thin transverse section of the diseased cord, several concen- tric zones are recognized; these correspond to the diiferent phases of the lesion, a. In the jjcriplieral zone, the traheculaj of the reticulum are thickened; the nuclei of the enlargements of the reticnhun are swollen ; the nerve-tubes are atrophied at the expense of the medullary sheath, the axis-cylinder being whole, i. In tJie second, or transitory zone, the size of the nerve-tubes is still less — indeed, in many the myelin has disaj)- ])eared, the axis-cylinder only remaining, which may be hypertrophied. The trabeculfo are more transparent, their contour less definite, and at certain j)oints they are replaced by bundles of long, delicate tibrilhe, analo- gous to those which are characteristic of common connective tissue. These are develo])ed at the expense of the meshes which contain the nerve-tubes, and the consequence is that the reticulated aspect of the Iiealthy neuroglia lias a tendency to disa])pear. c. In the central zone, that is, in the midst of the sclerosed patch, all traces of fibroid reticulum have gone ; there are neither cells nor trabecular; bundles of fibrils fill the alveolar interspaces, from which the myelin has entirely disappeared ; the axis-cylinders are atrophied to such a degree that Buy Droxia it is Ijard to distinguish them from the newly-formed fibrils. The persistence of these cylinders in the midst of OF THE IS'ERVOUS CENTRES. 247 the tissue which has undergone fibroid substitution, is, Dr. Charcot thinks, pecuhar to disseminated sclerosis. Tlie characters of the fibrillary tissue are particularly well exhibited in longitudinal sections. It is seen to be composed of parallel fosciculi, formed of delicate, opaque, smooth fibrils, rarely subdividing and anastomosing, but frequently interlacing, after the manner of felting, and which are col- ored by carmine. These characters enable us to distinguish it from the axis- cylinders, which are usually larger, transparent, and do not ramify. (Fig. 3.) Fig. 3. Kccent preparation from centre of a patch of sclerosis of the cord, colored 'by carmine and dilacerated. In the centre a capillary vessel with numerous nnclei. On either side axis-cylinders, sonic lar^e, others quite small, deprived of their myelin. The capillary and the axis-cylinders, strontily colored by carmine. The latter are perfectly smooth", and have no ramifications. Between the axis-cylinders, delicate fibrils of recent forma- tion are seen; on the right nearly parallel to each other, while in the centre and on the left, they form a sort of net-work, resulting from their interlacement, or anastomo- sis. They may be distinguished from the axis-cylinders by their diameter, which is much less, by their numerous ramifications, and by not being colored by carmine. Scattered nuclei are also visible : several are in connection with the fibrils, and others are of irregular form, from the action of the ammoniacal solution of carmine.— Chakcot. They may be distinguished, also, from the fibres of the reticulum by these beiug thicker, shorter, and always liaving branchlike processes. Finally, they differ from the elastic fibres by their swelling up from the action of acetic acid, and forming a transparent hyaline mas.-
|