I. HISTORICAL SURVEY The present name of the choroid is derived from the Greek: χόρΙον, membrane, and ##Ιδος, form, alluding to its vascular character, resembling that of the chorionic membrane, which envelops the fetus in the uterus. In this connection, it is interesting to note that the comparison established in the etymological derivation emphasizes the early recognition of the essential nature of this portion of the uveal tract. The fact that the main mass of the choroid is formed by vessels was also at a later period implied by Casserius and von Haller, who, respectively, called it the membrana sanguinolenta oculi and membrana vasculosa oculi.1 Rufus the Ephesian2 applied the term "chorion-like tunic" to that portion of the uvea which lines the sclera inwardly. Galen the Pergamenian3 regarded the middle coat of the eye as a continuation of the pia mater through the vascular investment of the