Methacrylate-embedded E16 embryo (ventral horizontal)
Figure 54. This slice is the most ventral that shows the lumen of the olfactory recess and the slit-like lumen of the lateral ventricle’s anterior horn. This slice most clearly shows two different migratory streams of migrating mitral cells. Both streams come toward the bulb from a subpial position in the basal telencephalon that is generously populated with fibers—the presumptive axons of the migrating mitral cells in the future lateral olfactory tract. In the anterior olfactory peduncle, most of the fibers and the cells turn sharply to the medial direction (dashed-line arrow), then curve forward toward the very thick olfactory nerve layer. The spindle-shaped cells on the lateral side of the bulb may have stayed on the lateral side (solid curved-arrows) or may be an extension of the medially migrating cells. It is interesting that the medial wing of the mitral cell migratory stream is only visible in this ventral slice. The dorsal slices indicate that there is a definite lateral wing to the mitral cell migratory stream. Are there functionally different mitral cells in the two wings of the migratory stream?