Wandering pigmented cells arising from the epithelium of the optic cup, with observations on the origin of the M. sphincter pupillae in the chick

Abstract

Nussbaum's' important discoveries of the origin of the M. sphincter pupillae in birds and mammals from the epithelium at the pupillarg margin of the optic cup and of the origin of the retractor lentis muscle in fishes froin the epithelium bordering on the choroid fissure are o l deep significance.His discoveries have recently been confirmed by Szili,' who has traced carefully the development of the sphincter pupillae muscle in man from the epithelium about the pupillary margin of thc optic cup.Herzog has also found a similar origin in a series of vertebrates.These authors have also studied the development of the dilator pupillae from the epithelial cells of the outer layer of the optic cup.The origin of the retractor lentis, the muscle of accommodation in fishes ( Salmo salar) , lead Professor Nussbaum to suspect that the ciliary muscle, the muscle of accommodation in higher vertebrates, might also be of epithelial origin.With this in view I attempted at the suggestion of Prolessor Nussbaum to determine if the ciliary muscle in the chick was of epithelial origin.It is a pleasure to express my thanks to Pro-