Abnormality in the optic nerve of albino mutant quails

Comparative studies were made between the optic nerves of albino and normal quails. The ipsilateral and contralateral retinofugal projections in the albino quail were similar to those in the normal quail. The abnormality of uncrossed projections in the visual pathways, which is found in albinos of many different mammalian species, was not present in the albino quail. The total cross-sectional area of the optic nerve was approximately 25% smaller in the albino quail than in the normal quail, whereas the fiber density was about 17% higher in the former. The total number of optic nerve fibers in normal and albino quails was therefore the same. Numerous unmyelinated fibers existed in normal and albino quail optic nerves, the ratio of myelinated to unmyelinated fibers being approximately 4:6. Axon diameters of myelinated and unmyelinated fibers in the optic nerves were smaller for the albino quail than for the normal quail. The number of the myelin rings in the albino quail slightly decreased compared with those in the normal quail.