The development of the irido-corneal angle in the chick embryo.

The iridocorneal angle of the chick embryo was examined by scanning electron microscopy from the 7th day to the 19th day of development. The mesodermal tissue situated between the corneal endothelium and the iris differentiated into trabecular cells. These cells formed a strip on the 9th day and enlarged on the 13th day to form long cellular fibres. The trabecular meshwork was recognizable on the 15th day and reached full development only on the 19th day. The development of the trabecular meshwork was probably much earlier than is usually described. It began with differentiation of the corneal endothelial cells and these cells acquired a multipolar cell body with long cellular processes. The last stage is probably regulated to avoid an abnormal development of the angle structure. These results can be correlated with those obtained in the morphological examination of the structure of the angle in congenital glaucoma and the "cleavage syndrome" of the anterior chamber.