ニワトリ視覚系の両側先天性異常例

A CONGENITAL MALFORMATION OF THE BILATERAL VISUAL SYSTEM IN A CHICK EMBRYO

緒言

　脊椎動物において，眼球あるいは視神経の欠損例ないしは小眼球症についての報告は，比較的しばしばみられる。しかし，鳥類については，Bellonci （1888）^1），　Bra—dis （1895）^2），　Edinger et al （1899）^5），　Brouwer （1918）^3），Mikami （1953）^9）等，その報告は比較的少ない。

　著者は両側視神経を安全に欠如するきわめて興味あるニワトリ胎児を入手する機会を得たので，この例の視覚系と眼筋支配中枢につき報告する。

A chick embryo just before the hatching, of which the both eyeballs show a strong malformation was fixed with 10% formalin, embedded in paraffin, sectioned at 10μ and stained with the BODIAN's method and the NISSL's method.

In the retina, the pigment layer is found on both sides but the cerebral layer is lacking at all. The optic nerve, the optic chiasma and the optic tract are completely lacking. The lateral geniculate body and the optic tectum are on both sides strongly under-developed. In the optic tectum of the both sides, the 1 st layer (RIS, 1899) is lacking and the 2 nd to the 5 th layers are thinner in comparison with the normal development. The oculomotor, the trochlear and the abducent nuclei are under-developed, especially the latter two nuclei of the right side are strongly reduced, in comparison with the normal case. The Nucleus arciformis (KOIKE-GAMI, 1933) is also under-developed, particularly on the right side.

The optic vesicle can induce the lens, without the differentiation of the optic cup. The optic nerve is closely related with the normal develop-ment of the lateral geniculate body as well as the optic tectum.