The birth canal occupies a singular position in the depth-psychological corpus as the somatic threshold between intrauterine existence and autonomous life, carrying freight far exceeding its anatomical reference. Stanislav Grof, its most systematic theorist, places the passage through the birth canal at the structural core of his Basic Perinatal Matrix III (BPM III), where the cervix has opened and propulsion has begun but liberation remains incomplete — a condition he maps onto experiences of volcanic aggression, sadomasochistic imagery, and the titanic struggle between life and death. The completed transit, corresponding to BPM IV, becomes the template for all later experiences of sudden liberation following extreme compression. Otto Rank anticipates this framework by grounding the primal anxiety in the pressure and displacement of the birth process itself, the canal functioning as the site where paradise is definitively lost and the long compensatory detour of the libido begins. Rick Strassman extends the analysis into neurochemistry, proposing that the catecholamine surge of vaginal delivery triggers pineal DMT release, rendering the birth canal a biochemical as well as psychological initiatory passage. In archetypal astrology (Dennett, Tarnas) the passage is associated with Plutonic transformation: breakdown, descent, and regenerative emergence. Jung’s earlier corpus treats birth symbolism more obliquely, through water and enclosure imagery, while Cooper employs the failed or aborted passage as a figure for developmental arrest. The term thus anchors debates about perinatal memory, transpersonal psychology, somatic trauma, and the psychochemistry of consciousness.