The anatomy of the nervous system, from the standpoint of development and function . das the restiform body becomes clearly defined (Fig. 101). As one would expect from the fact that there is no sharp line of separation between thespinal cord and medulla oblongata, some of the fibers of the cuneate fasciculus end in thesubstantia gelatinosa (here known as the nucleus of the spinal tract of the trigeminal nerve)and in the remnant of the head of the posterior gray column (Fig. 100). There are threesmaller gray masses within the funiculus cuneatus: (1) the external round nucleus, an iso-lated por
The anatomy of the nervous system, from the standpoint of development and function . das the restiform body becomes clearly defined (Fig. 101). As one would expect from the fact that there is no sharp line of separation between thespinal cord and medulla oblongata, some of the fibers of the cuneate fasciculus end in thesubstantia gelatinosa (here known as the nucleus of the spinal tract of the trigeminal nerve)and in the remnant of the head of the posterior gray column (Fig. 100). There are threesmaller gray masses within the funiculus cuneatus: (1) the external round nucleus, an iso-lated portion of the substantia gelatinosa, near which it is situated; (2) the internal roundnucleus, more variable in position; and (3) the accessory or lateral cuneate nucleus superficialto the main nuclear mass. Funiculus gracilis Nucleus gracilis Spinal tract of trigeminalnerve Nucleus of spina! tractofN. V Dorsal motor nucleus of Jjyvagus Nucleus of hypoglossalnerve Decussation of mediallemniscus Lateral reticular nucleus Medial accessory olivarynucleus Ventral external arcuatefibers. Funiculus cuneatusXuclens cuneatusCentral canal Internal arcuate fibersReticular substance Dorsal spinocerebellar tract ^iL___}entra! spinocerebellar trad Ventral fasciculus proprius Hypoglossal nerve Pyramid, corticospinaltrad Fig. 99.—Section through the medulla oblongata of a child at the level of the decussation of themedial lemniscus. (Pal-Weigert method.) (X 6.) The Medial Lemniscus and its Decussation.—The great majority of fiberswhich arise from the cells in the nucleus gracilis and nucleus cuneatus sweepventromedially in broad concentric curves around the central gray substancetoward the median raphe (Fig. 99). As has been stated on a preceding page,these are known as internal arcuate filers, and as they cross those from theopposite side in the raphe they form the decussation of the lemniscus (decussatiolemniscorum, sensory decussation). After crossing the median plane they turnrostrally
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectnervoussystem, bookye
