Methacrylate-embedded E16 embryo (dorsal horizontal)
Figure 51 is the dorsal horizontal slice through the future olfactory bulb. The most superficial layer is the very thin olfactory nerve layer that blends with the next layer of spindle-shaped cells that are migrating within the plane of the section in an unbroken arc around the olfactory evagination. The possibility exists that some of them are AOB output neurons migrating from a medial germinal source near the septal NEP (dashed arrows) to a lateral and dorsal position in the bulb parenchyma. There are many more spindle-shaped cells on the lateral side of the slice extending all the way back into the basal telencephalon—the presumptive mitral cells migrating from germinal sources in the basal telencephalic NEP (curved solid arrows). The lateral olfactory tract is a prominent accumulation of fibers just beneath the brain surface bordering the basal telencephalon; the spindle-shaped cells migrating in the layer are probably mitral cells from a more posterior basal telencephalic germinal source.