. A manual of diseases of the nervous system. legs only are affected, the sclerosisoccupies the whole of the columns in the lumbar region (Fig. 119), butit is often slight in the anterior parts of the postero-external columns,which may even be free from sclerosis; also in the middle of thesecolumns many more nerve-fibres may be seen than elsewhere. Thesclerosis is most dense in the j)art adjacent to the posterior cornu,through which the posterior root-fibres run, and near the surface of thecord (Fig. 119, d 12). Above the lumbar enlargement the affection ofthe postero-external columns graduall
. A manual of diseases of the nervous system. legs only are affected, the sclerosisoccupies the whole of the columns in the lumbar region (Fig. 119), butit is often slight in the anterior parts of the postero-external columns,which may even be free from sclerosis; also in the middle of thesecolumns many more nerve-fibres may be seen than elsewhere. Thesclerosis is most dense in the j)art adjacent to the posterior cornu,through which the posterior root-fibres run, and near the surface of thecord (Fig. 119, d 12). Above the lumbar enlargement the affection ofthe postero-external columns gradually ceases, but the degeneration isintense in the postero-median columns, and has the distribution of anascending degeneration, as it in fact is, receding from the commissurein the upper cervical region. (Compare Fig, 119 with Fig. 74, p. 177.)In other cases the external band of sclerosis, adjacent to the cornu,continues separate through the dorsal cord and even through thecervical enlargement (Fig. 120) ; the median degeneration then extends. Fig. 120.—Tabes with ataxy of the arms as well as the legs. Sectionof cord in cervical region, showing sclerosis of the columnand root-zone of col. Degeneration of left ant. cornu. up to the commissure throughout the cervical region, just as does thesecondary degeneration that results from a cervical lesion (see Fig. 76,p. 178). But in the ceivical enlargement, the unaffected area in theanterior part of the postero-external column is usually much largerthan in the lumbar enlargement. In rare cases, of severe and long duration, the j^osterior columns areoccupied by connective tissue in their whole extent from one end of thecord to the other. A few fibres of the posterior roots and a fewvertical fibres near the commissure may alone be recognisable. Aninstance of such almost complete sclerosis is shown in Fig. 121. On the other hand, in slight cases, in which the disease is still in thefirst, or in the commencement of t
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