. A manual of diseases of the nervous system. nding level of the fourth pair of sacral nerve-degeneration of the ^^ .j,- ^^y -^ bearing thecolumn spreading out against the • v-^ » _ y & commissure. The other figure is USual proportion to the lateral tract,from the lower dorsal, and shows j^ ceases about the mid-dorsal region,degeneration ot the pyramidal ^^ , „ ,, „, ,, i j^-. tracts, anterior and lateral. Most of the fibres pass through the anterior commissure to the oppositeside, either entering at once the grey matter, or passing first to thelateral The latter is probab
. A manual of diseases of the nervous system. nding level of the fourth pair of sacral nerve-degeneration of the ^^ .j,- ^^y -^ bearing thecolumn spreading out against the • v-^ » _ y & commissure. The other figure is USual proportion to the lateral tract,from the lower dorsal, and shows j^ ceases about the mid-dorsal region,degeneration ot the pyramidal ^^ , „ ,, „, ,, i j^-. tracts, anterior and lateral. Most of the fibres pass through the anterior commissure to the oppositeside, either entering at once the grey matter, or passing first to thelateral The latter is probably the course of most of the fibreswhen the pyramidal decussation is small. Whether any fibres endin the grey matter on the same side of the cord we do not know. Disease of the brain destroying the motor cortex, or the fibres which * Dejerine and Thomas, Compt. Rend., 1896, p. 157. Russell traces it to the5th segment. t Although this is probable there is no definite evidence of it except in the sacralyegiou (Russell, Brain, 1898).. Fio: 72—Ascending and descend-ing degenerations from myelitisof the mid-dorsal region; theupper section is from the lower STETJCTUEE. 21] descend from it to tlie pyramids, causes desc^nrling usually limited (at least in conspicu-ous degree) to tlie related pyra-midal tracts,—anterior on tlie sameside, lateral on the opposite side(Fig. 73). But in many cases sligMdegeneration lias been also foundin the lateral tract on the same side,extending into the lumbar it is probable that somefibres of each anterior pyramidfind their way to the lateral tract onthe same side, and descend to thecorresponding limbs, especially tothe leg. This degeneration of thelateral tract on the same side asthe lesion is sometimes very markedjust below the decussation of thepyramids, and is therefore not dueto any lower re-decussation in thecord.* Muratoff has shown, byextirpation of the cortical areas forthe extremities, that a bundle from
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