Section through the medulla at the level of the great sensory decussation (Mf). The latter is the decussation of the medial fillet, and is seen ventral to the central canal. The fibres are derived from the gracile (Ng) and cuneate nuclei (Nc), and sweep round the central canal to form the arcuate bundles (Arc). The fasciculus gracilis and   fasciculus cuneatus (Fc) are seen, the latter larger and more conspicuous since it extends up to a higher level before terminating. The spinal nucleus of the fifth nerve (V) is clearly outlined, and, superficial to it, the spinal tract of the fifth nerve (Sp). Laterally at the surface are seen the dorsal (Scd) and ventral spino-cerebellar tracts (Scv), of which the former stands out rather sharply. Below are the pyramids (P) on the surface of which is a thin zone of grey matter, the arcuate nucleus (Na). Immediately dorsal to the pyramid is the lower extremity of the olivary nucleus. 

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