A manual of diseases of the nervous system . region (third cervicalsegment) this tract lies farther forwards, so that the pyramidal tractcomes up to the surface close to the posterior cornu (Fig. 68, c. 3),and here, if the tract is small, there may be a depression on the sur-face. In the lower part of the dorsal cord there is a similar move-ment forwards of the cerebellar tract, so that the pyramidal tractagain comes in contact with the surface posteriorly (Fig. 68, d. 12),and, as the cerebellar tract ceases at the last dorsal nerve, the pyra-midal tract extends up4o the surface throughout the
A manual of diseases of the nervous system . region (third cervicalsegment) this tract lies farther forwards, so that the pyramidal tractcomes up to the surface close to the posterior cornu (Fig. 68, c. 3),and here, if the tract is small, there may be a depression on the sur-face. In the lower part of the dorsal cord there is a similar move-ment forwards of the cerebellar tract, so that the pyramidal tractagain comes in contact with the surface posteriorly (Fig. 68, d. 12),and, as the cerebellar tract ceases at the last dorsal nerve, the pyra-midal tract extends up4o the surface throughout the lumbar enlarge-ment (Fig. 63, li 4). The inner side of the tract is in contact with thehinder part of the posterior cornu, near the surface, throughout theentire length of the cord, but further forwards it is separated from theneck of the cornu and intermediate grey substance by a layer of nerve-fibres, termed by Flechsig the lateral limiting layer (l. l. Fig. 64).* Hadden and Sheirington, Brain/ viii, 502, pi., fig. 1. STRUCTURE. 173. Among the fibres of tlie pyramidal tract, in the dorsal and cervicalregions, degeneration reveals a few other fibi*es that belong chieflyto the cerebellar tract. The lateral pyramidal tract diminishes insize from above downwards as its fibres end by entering the greymatter ; those that extend lowest (for the leg) occupy the posteriorpart of the tract in the cervical region. The fibres curve inwardsalong the septa that extend from the grey matter into the lateralcolumn, and they enter the grey matter between the anterior andposterior cornua. They pass inwards and forwards in the anteriorcornu, and are then lost in the complicated structure of the greymatter. Their probable termination will be considered presently. The anterior or direct pyramidal tract (called also the column ofTiirck) descends the cord in the innerpart of the anterior column, adjacentto the anterior median fissure. Itsexact form and size vary; usually itbounds the fissure on
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnervoussystem, bookye
