. A manual of diseases of the nervous system. so be general, or itmay be greatest in the root-zone and in the posteriormedian columns. The cer-vical root-zone never ? es-capes, as it often does intabes. The degeneration of thelateral columns always in-volves the pyramidal tracts,and is most intense in theirposition. It is not, how-ever, Umited to them. Itusually extends outwards tothe periphery of the cord,even where the pyramidaltract does not reach thesurface, thus involving thedirect cerebellar tract; andit also extends forwards atthe surface, so as to con-stitute a band of annularsclerosis
. A manual of diseases of the nervous system. so be general, or itmay be greatest in the root-zone and in the posteriormedian columns. The cer-vical root-zone never ? es-capes, as it often does intabes. The degeneration of thelateral columns always in-volves the pyramidal tracts,and is most intense in theirposition. It is not, how-ever, Umited to them. Itusually extends outwards tothe periphery of the cord,even where the pyramidaltract does not reach thesurface, thus involving thedirect cerebellar tract; andit also extends forwards atthe surface, so as to con-stitute a band of annularsclerosis, which varies iathickness in different partsof the cord and in differentcases (rigs. 141, 142). In * For the sections from which the drawing is made I am indebted to Dr. Pitt(who prepared them) and the late Dr. Moxon, under whose care the patient died inGuys Hospital. The case (full details of which will be found in a recent volume ofthe * Guys Hospital Reports ) is one of a series of five cases (four brotherg and « HEEEDITARY ATAXY. 527. the inner part of the anterior column there may be a distinct areaof degeneration in the position of the anterior pyramidal tract. Thisis seen in Fig. 140, in which this tract extends unusually low in thecord, and is distinctlydegenerated m theupper part of thelumbar of the poste-rior vesicular columnhas been found a. :o- fciated with that of thedirect cerebellar abnormal ap-pearances have beenseen in the nerve-cellsof the anterior cornuain some cases, but as arule these are normal,and the grey matterpresents no other dis-ease. It is very likely,however, that futureobservations will revealthe occurrence ofchanges in the nerve-cells of the posteriorhorns, such as are metwith in tabes. The pia mater over the posterior columns has been found posterior nerve-roots usually present some degeneration of theirfibres; this may be partial (Fig. 143, b), or may amount to totaldestruction of the fibres (as
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