Systems Atlas Project
2026-07-31 · stress-test
Cranial nerve placement
diagnostics/2026-07-31-cranial-nerve-placement
The entry
What went wrong, and what was done about it.
Issue
Cranial nerves are placed in the peripheral nervous system on anatomical grounds. CN I and CN II are histologically central nervous tissue, and CN II is a tract of the diencephalon rather than a peripheral nerve. Placing them peripherally makes the division fail on histological criteria while passing on anatomical ones, which means the division is only mutually exclusive once it is fixed which criterion governs.
Resolution
Left standing. Anatomical placement is applied consistently across the whole division rather than making an exception for two nerves, on the grounds that a consistent rule with a recorded failure is more useful than an inconsistent rule with none. The criterion question is the real issue and is not settled by this entry.