Fine structures of the inner ear vessels in the guinea pig fetuses were observed by scanning electron microscope with casting method using Mercox resin. In 32 days fetus, the vascular pattern of cochlea and vestibule differed in appearance from those in adult. With olders than 40 days, the vascular patterns closely resembled those of adult. The vestibule in guinea pig, as well as human, advanced in development of blood vessel earlier than cochlea. The fetus blood vessel pattern was denser than in adults. It was assumed that the loss of blood vessels occurs in the inner ear after birth. Imprints on the corrosion casts of blood vessel in fetus were observed more deeply than in adult. The present indicates those structures were beneficial for their. development.
