Henry Gray (18251861). Anatomy of the Human Body. 1918.
spinalis, and its apex directed toward the posterior gray commissure. It increases in size from below upward, and consists of long thin fibers which are derived from the posterior nerve roots, and ascend as far as the medulla oblongata, where they end in the nucleus gracilis.
The fasciculus cuneatus (tract of Burdach) is triangular on transverse section, and lies between the fasciculus gracilis and the posterior column, its base corresponding with the surface of the medulla spinalis. Its fibers, larger than those of the fasciculus gracilis, are mostly derived from the same source, viz., the posterior nerve roots. Some ascend for only a short distance in the tract, and, entering the gray matter, come into close relationship with the cells of the dorsal nucleus; while others can be traced as far as the medulla oblongata, where they end in the gracile and cuneate nuclei.
FIG. 673 Formation of the fasciculus gracilis. Medulla spinalis viewed from behind. To the left, the fasciculus gracilis is shaded. To the right, the drawing shows that the fasciculus gracilis is formed by the long fibers of the posterior roots, and that in this tract the sacral nerves lie next the median plane, the lumbar to their lateral side, and the thoracic still more laterally. (Poirier.) (See enlarged image)
FIG. 674 Descending fibers in the posterior funiculi, shown at different levels. A. In the conus medullaris. B. In the lumbar region. C. In the lower thoracic region. D. In the upper thoracic region. (After Testut.) (See enlarged image)
The fasciculus gracilis and fasciculus cuneatus conduct (1) impulses of conscious muscle sense, neurons of the second order from the nucleus gracilis and nucleus cuneatus, pass in the median lemniscus to the thalamus and neurons of the third