The first thing seen is the red reflection of the choroidal vessels showing through the transparent retina; and when the eye observed is directed upward and inward, we see the usually circular disc of the optic nerve, encircled by a double ring, cream-colored, or very faintly roseate or grey, and surrounded by the red choroid. The two rings are the apertures in the choroid and sclerotic, of which the former is the smaller. From out this disc we see springing the retinal artery and retinal veins, sometimes centric, at others excentric, in their passage. The artery is easily recognized as being somewhat smaller in calibre, and of a lighter red. The artery usually divides into a superior and inferior branch, each of which subdivides forthwith into two secondary branches, and these again continue to subdivide, dichotomously, running forward to the anterior limits of the retina. The veins, which are somewhat larger and deeper colored, usually pierce the disc of the optic nerve in two trunks. Pulsation may occasionally be detected in the veins by watching carefully their color, which seems to change at each impulse just where they pass over the edge of the optic disc and bend to pierce the nerve. Fuller details of the ophthalmoscopic appearances of healthy eyes, both human and animal, will be found in Zander's treatise, excellently edited and translated by Mr. R. B. Carter, of Stroud. In the healthy eye the aqueous humor, lens, and vitreous humor are clear, and do not in any way obstruct the passage of the light. It is otherwise in disease; and this brings us to the discussion of some of the practical applications of the ophthalmoscope. Here, perhaps, I may be permitted to quote some of the {124} paragraphs of a paper which I read lately on the subject before the Hanveian Society: [Illustration: Interior of eye. ]