Methacrylate-embedded E14 embryo (intermediate sagittal)

Figure 18 is an intermediate sagittal slice through a part of the telencephalon where presumptive olfactory nerve fibers are contacting the brain surface that will grow outward into an olfactory bulb.  Some of the cells outside the olfactory NEP are no doubt the AOB output neurons.  The curved arrows exiting the ganglionic eminence point out spindle-shaped cells that appear to be migrating within the section plane—most probably heading anteriorly.  In this slice, there is a continuity between the olfactory nerve and the olfactory epithelium.  Indeed, fibers can be seen exiting the epithelium to join the nerve.  The large cells inside the nerve are presumptive supporting cells (glia) that nurture the growing olfactory axons.  The olfactory nerve makes contact at various points with the brain surface where there is ample opportunity for cellular exchange between the brain and the periphery.