1. Beadles.-Brain, Vol. XXX, p. 285, 1907.
2. Bramwell.-Edinburgh Med. Ji., Vol. 1X, p. 152, 1889.
3. Conway.-Brit. Jil. of Ophthal., Vol. X, p. 78, 1926.
4. Freund. -Klin. Monatsbl.f. Augenheilk., Vol. LVI, p. 468, 1916.
5. Hutchinson.-Trans. Ophthal. Soc., U.K., Vol. IX, p. 152, 1889.