"I have been induced, for my own satisfaction, (in consequence of some observations made by Sir George Sinclair, who had witnessed its effects on patients under Dr. Turnbull's care), to give a very extended trial to the prussic acid in cases of ophthalmic disease which might be considered suitable for its application, and desire that the results of some of the cases should be submitted to the consideration of those of our profession who may take an interest in the subject I have, therefore, made out a report of the following cases. In our present state of knowledge it is impossible to explain the _modus operandi_ of the prussic acid; it will be sufficient, meantime, to observe accurately, and merely give the results of treatment. In what kind of cases it will be found most suitable can only be determined by further inquiry and experience. If, however, the results prove permanent, the prussic acid must occupy a very high place amongst our remedial agents; and, possessing stimulant properties of a peculiar character, it may prove useful under many circumstances where diseases of the eye are not readily amenable to ordinary treatment. "CASE 1. "J. MACKAY REAY, aged 11 years. Diffused opacity of the cornea, the result of a protracted attack of scrofulous ophthalmia. The vapour of strong prussic acid was applied, daily, for thirteen days, by exposure of the eye to it, during which period the cornea gradually got transparent. On the fourteenth day no remains of former opacity existed, and the vision of that eye was perfectly restored. "CASE 2. "MARGARET MACKAY, Thurso, aged 12 years. Severe rheumatic ophthalmia, of three weeks' duration. She complains of deep-seated aching pain in the eye-ball, greatly aggravated in the evening and through the night; no apparent disorder of the general health. The ordinary remedies were used, viz., leeching, blisters, calomel, and colchicum: they appeared to give no relief. The prussic acid was applied, daily, for about ten days; the relief following each application was extraordinary; the pain was trifling for the rest of the day. At the expiration of twelve days the intolerance of light, the injected state of the vessels on the sclerotica, and the other symptoms, entirely disappeared; and since September the little patient has continued quite free from any symptom of her former ailment. "CASE 3. "A girl, named MUNRO, from Mount Pleasant. Albugo of corneæ in both eyes, the result of an attack of acute conjunctival ophthalmia, which she had about two years ago, whilst residing in Dundee, where various means were tried for her relief. Vision was almost completely destroyed; she could not distinguish the outlines, form, or colours, of objects presented to her. At her own urgent request, but without holding out any prospect of her being benefited by it, the prussic acid was applied, daily, for about six weeks.