The inner ear is generally considered to be nourished by the endartery from the vertebral artery system.A study of 39 adult human temporal bones revealed individual variation on the microfissures and such were the fracture-line like structures observed between the horizontal portion of the facial canal and the horizontal canal ampulla.These microfissures house a structure resembling the blood vessels and some can be definitely identified as capillaries or arteries by the content of erythrocytes and by relationship to the Harver's canal. Of 39 temporal bones studied, 15 had apparent blood vessels in the microfissures between the posterior canal ampulla and the round window niche and between the horizontal canal ampulla and the horizontal portion of the facial canal.These findings indicate that inner ear blood flow from the vertebral artery has a collateral circulation with the external carotid artery via these microfissures, and also that these collaterals have individual variations.