Excerpt from A Treatise on the Diseases of the Nervous System The object-lens should have a focal distance of about two inches, and it should be held so as to bring the focus on the pupil. The lamp is placed behind and a little to one side of the eye to be examined. In order to see the optic disk, the patient is told to look at the ear of the observer on the side opposite to the eye being examined. In this way the axis of vision is directed inward, and the optic disk readily brought into view. These examinations are made in a room lighted only by the lamp used in the processes. It is sometimes necessary to dilate the pupil with atropia, in order to obtain a view of the disk, but experience and tact will generally enable the observer to dispense with this rather dio agreeable procedure. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.