a fiber system, termed Reichbündel by E. Zuckerkandl, that descends from the transparent septum in front of the anterior commissure toward the base of the forebrain; it contains precommissural fibers of the fornix, fibers from the septum to the hypothalamus and innominate substance, as well as fibers ascending to the septum and hippocampus from the hypothalamus and midbrain; it bears no special relation to the sense of smell.