The Inner Limiting Membrane of the Retina.

TmE micro-anatomy of the region between the retina and the vitreous has been a source of discussion and interest for more than a century. Work has, in general, been concerned with the inner surface of the retina and has involved extensive investigation of what is normally termed the inner limiting membrane. The basis for this name was very probably provided by Pacini, who referred to a homogeneous structure on the vitreous surface of the retina as the membrana limitante. The same author, however, mentions at least twelve other workers who apparently preceded him with morphological studies on the retina (Pacini, 1845). Indeed, earlier references to the inner retinal surface can readily be collected; for example, Gottsche (1836) recognized a lamellar tissue in close relationship to the inner nervous elements of the retina and Michaelis (1837, 1842) wrote of what he called the "serous inner layer" of the retina. It is difficult to be certain when ordered structure was first observed within the region of the membrana limitante, but the first description is almost certainly due to Hannover (1840), who wrote of a glass-bodied membrane composed of large, transparent, six-sided "cells". Pacini also described a similar appearance, but the formation and minute relations of the membrane were not considered in greater detail until the description of the radial fibres by Heinrich Muller (1851) prompted both Scbultze and Schelske to suggest that the mosaic of cells described by Hannover was in fact related to the flat vitrad ends of the radial fibres. Schultze went so far as to state, in a classical work on the structure and function of the retina, that the membrane is formed by these fibres (Schultze, 1859); Schelske was content merely to write that the morphology of the two structures did, to some extent, correspond, and that the suggestion made by Schultze was a possibility. The same author went on to show that the average diameter of the clear spaces in the mosaic formation varied approximately between 3 x 20 microns, and further that the spaces were elongated in the long axis of the great vessels to a maximum size of 42 microns (Schelske, 1863). In 1871, the great anatomist Gustav Retzius published the first of two articles on the inner limiting membrane; he first extensively reviewed the existing work on the subject and then went on to describe experiments on