Among the matters of interest which were brought before the British Medical Association, at the recent Glasgow meeting, was an account by Mr. Brudenell Carter of a method which he had devised of opening the sheath of the optic nerve behind the eye, for the relief of pressure within this sheath and within the cavity of the skull. The brain is invested by firm membranes, which secrete a certain amount of fluid and are continued down to the eye in the form of a sheath which surrounds the optic nerve; and, whenever the pressure within the cavity of the skull is increased, as by the growth of a brain tumor, or even by excess of secretion from the membranes themselves, a superabundance of fluid is apt to find its way down the nerve sheath to the level of the eye, to subject the optic nerve to injurious pressure, and, in many cases, to destroy the sight. It not infrequently happens that the pressure within the brain cavity may be increased by temporary or curable causes, which, nevertheless, continue in action sufficiently long to produce permanent blindness, even although the patient may, in other respects, recover. In view of these conditions it was suggested by Dr. De Wecker, of Paris, sixteen or seventeen years ago, that it might be possible to open the optic nerve sheath, and thus not only to relieve the nerve from pressure and to preserve it from injury, but also, on account of the position of the eye relatively to the brain cavity, to drain the latter by gravitation, and to relieve the brain as well as the eye. Dr. De Wecker made two endeavors to accomplish this object, but he tried to feel his way to the optic nerve without the aid of sight, and to incise the sheath by means of an instrument carrying a concealed knife, capable of being projected by means of a spring. The risks of failure, and, still more, the risks of inflicting irreparable injury upon the nerve, were such that he only attempted his operation in two well nigh hopeless cases, and only one attempt to follow his example has been recorded. Mr. Carter's attention was called to the matter last year by a case in which the diminution of pressure within the optic nerve sheath was manifestly desirable; and he devised a method of operating by which the sheath could be exposed to view, and the object attained with certainty, under the guidance of sight at every step of the process.