"It is of frequent occurrence to find the capsule of the lens stained with black spots; these are stains left by the uveal pigment, and occur usually after an attack of iritis, when the iris has been in contact with the lens. When the iris has been adherent, a complete ring of pigment may often be seen on the surface of the lens. A day's experience at any ophthalmic elinique can mostly show examples of this condition; but it is only when these deposits are numerous, and in the central line of vision, that they become troublesome. They are then met with as the sequences of severe choroido-iritis, and usually coincide with further mischief in the vitreous and choroid.

"The vitreous, under the influence most commonly of choroiditis, and usually syphilitic choroiditis, presents alterations of the most striking character for ophthalmoscopic observation. The patients who offer these changes complain usually of considerable dimness of sight, which on examination is found to include both diminution in the acuteness of visual perception, and restriction in the field of vision, or extent of any object seen at once. The great source of trouble to them is, that when they lift the eye or move the head, black corpuscles, or streaks, or Webs float before their eyes, and obscure the object at which they are looking; and when the eyes are kept still, these fall again and disappear. Examine now the eyes of such an one, and you will see that the phenomena

described are due to the existence of actual shreds, corpuscles, or webs of fibrous and albuminous exudation, which float in the vitreous, and at each motion of the eye rise in clouds and obscure the fundus, so that you can barely see it, or perhaps not at all. These conditions, I say, are mostly specific, but not invariably. They are sometimes the result of scrofula, and probably of other forms of choroiditis."

Here, then, are a large number of cases in which the ophthalmoscope transports us at once from the regions of the known to the unknown. There are other classes of cases equally striking. Let me take illustrative examples. Two persons apply for advice, complaining that the sight has been gradually growing more and more dim, perhaps in one eye,-it may be in both. The progress of the disease has been insidious and nearly painless. The eyes are to all external appearance healthy, except probably that in both patients the pupils are partially dilated and sluggish. The ophthalmoscope helps us to solve the problem.

The one is a case, it may be, of slow atrophy of the optic nerve, proceeding from central disease of the brain-from pressure on the optic tracts of nerve within the skull, or from defective nutrition following losses of blood. We find the nerve glistening white and slightly cupped, the arteries small, the fundus otherwise healthy. In the other we recognize at once, in the fulness of the veins, their pulsation, and the marked excavation of the optic disc, the indications of excessive tension of the eyeball and undue pressure of the nerve. The first requires careful constitutional treatment and a long course of studied hygiene and medication; the second calls for direct and immediate

In the

interference, with the view of relieving the intra-ocular pressure. diagnosis of this great class of glaucomatous disease of the eye-disease

characterized by loss of vision, sometimes slow and sometimes rapid, but always characterized by definite ophthalmoscopic signs: cupping of the dise, pulsation, fullness of the veins, and it may be more or less haziness of the transparent media-ophthalmoscopy has rendered a most brilliant and inestimable service. Prior to the introduction of the use of this instrument the disease was of an unknown pathology; its results were fatal to vision, but there were no means of diagnosing the conditions attending the earlier stages, and blindness followed almost certainly and inevitably. The investigation of the disease has brought us a remedy in the excision of a portion of the iris-a practice introduced by Von Gräfe, of Berlin, and of which the success is in suitable cases most gratifying.

Another series of examples may be chosen to illustrate the application of ophthalmoscopy. I avoid giving details here, but it is perhaps right to say that these are not fanciful sketches, but notices of cases in my experience and taken from my note-books of practice. Two persons are asking for advice as to the management of their eyes for short-sightedness. Are both to receive the same advice? The ophthalmoscope alone can furnish positive data. With this we may discover a staphylomatous condition of the back of the eye, a bright excentric margin around the optic disc and edged with black pigment. Examining it closely, we may find that this pigmented edge gives evidence of progressive inflammation at the back of the eye, and extending to continuous and increasing atrophy and retrocession of the coats of the eye. This person is in danger of becoming rapidly made short-sighted or of losing sight altogether. We must prohibit the use of concave glasses for a certain length of time, and must adopt active and effectual measures for subduing the atro phic inflammation. In the other patient the ophthalmoscope may show us but little stretching or waste, and that not

progressive, and will enable us then to calm his fears, to prescribe appropri ate glasses, and to dismiss him to his occupation with ease of mind and safety. So with sudden loss of sigh: from intra-ocular hæmorrhage, the ophthalmoscope gives us information which could never have been guessed at without it, and guides us, not only to the local knowledge, but to the constitutional information essential for cure.

There are certain conditions of the eye which may warn any one that it is desirable that the condition of the vision ought to be investigated by the ophthalmoscope. Rapidly increasing short-sightedness is one of the most marked, and when this becomes associated with weakness of sight and loss of acuteness in the perception of small objects, the warning is very urgent. A diminution in the field of vision is another important indication of internal changes in the eye, of which only the ophthalmoscope can detect the true nature. It would be difficult, perhaj :, to say whether more mischief is done and more suffering is caused by the total neglect of such symptoms or by their ignorant palliation by the aid of common spectacles, chosen empirically, because they facilitate vision for the time. The great use of the ophthalmoscope, then, is this: that it arms us with an instrument of precision, by which we can determine the precise local condition of the parts of the eye in which the function of sight is resident and through which it is regulated. If it cannot do all that we might ask, it is because the sense of sight is in truth a cerebral function, of which the eye is only an instrument; and in dealing with cerebral affections of the sight, it can indeed give us information which without it we should lack, but it leaves still to be desired more inti mate acquaintance with first causes which at present we can only discus inferentially. To the amateur in science, and to the lover of nature, it discloses an exquisite spectacle, unknown till now, that carries observa