coarse encephalic lesion, the existence of papillitis renders the diagnosis almost infallible, though, so far, we cannot locate the lesion from any signs given by the ophthalmoscope.

A clear distinction as to location of initial lesion lies in the monocular existence of papillitis, which, quite certainly, proves the pressure to be this

side the chiasm, and so, probably, orbital in origin. But there have been at least six well-attested cases of cerebral tumor in which only one optic nerve was affected, and these are enough to make one modest.

Prognosis. As regards sight, it is usually unfavorable, though every special case requires the aid of the general diagnosis and prognosis, to

DISEASES OF TIIE OPTIC NERVE.

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become definite or approximately accurate. In pronounced papillitis it is not, as a general rule, usual to find any, or but little and slow, regaining of lost visual power. It is considered well to retain what is left.

Treatment. As papillitis is entirely symptomatic, its treatment is one with the general disease causing this and other symptoms, from the study of all of which only a trained judgment will be able to formulate the right therapeutic agent. The iodides and bromides will be used in encephalic lesion, mercurials and iodides in syphilis, tonics in menstrual disorders, etc. When the indications are that the pressure is orbital in location, diagnosis and treatment are of the extremest doubt and uncertainty. In tobacco amblyopia, total abstinence is imperative.

ATROPHY OF THE OPTIC NERVE.

Causes. It is believed that atrophy of the nerve may be idiopathic ("primary"), but the vast majority of cases are "secondary," proceeding from retinal or from cerebral lesion, or from pressure along the course of the nerve, in most of which cases it succeeds some form of neuritis. The greater number of cases are certainly due to diseases of the brain and spinal cord, while tobacco, alcohol, traumata and syphilis do not fail each to bring his quota. Its connection with locomotor ataxia is not to be forgotten.

Symptoms.-Visual acuity is lessened, color perception is disordered and the field retracted in varying degrees, according to the progress of the disease. There is no pain, and seldom photophobia.

Diagnosis. The ophthalmoscope shows, usually, a pallor of the disc, instead of the rosy, healthy hue of the normal disc, though instead of this dead paleness, it has a distinct bluish hue sometimes, and, too, a grayish or yellowish cast. Its outlines have a hard sharpness, producing altogether a striking or staring appearance; the lamina cribrosa is usually visible. It must be remembered that mere paleness may exist without atrophy, as in anæmia and tobacco amblyopia, but the loss of transparency, hardness of outline, etc., must be considered with other symptoms. The color of the atrophied disc is not, certainly, indicative of special causes.

Prognosis. Probability of retaining the vision yet left is small. The progress is generally from bad to worse.

Treatment. We must seek the cause. Locally, the weak constant current and strychnia hypodermatically injected may be tried till proved of no avail.

GENERAL DISEASES.

GLAUCOMA.

Cause. Glaucoma is characterized by an increase of intraocular tension or pressure above the normal. All the catalogue of woes is, in this disease, a simple result of this fundamental condition. There are many theories, about one to every writer, hoping to explain the origin of this heightened tension; but two chief ones have occupied the most attention. They might be spoken of as the theory of hyper-secretion and that of the retention of the intraocular fluids. To irritation of the nerves governing the secretory functions was attributed the excessive amount of fluids. The retention theory has probably the greater number of supporters at the present time, though it is assuredly open to severe criticism. It is well known that the effete fluids pass out of the globe principally by the way of the ligamentum pectinatum and canal of Schlemm, and in glaucomatous eyes it is found that the periphery of the iris lies in contact with the cornea and thus dams the outlet. Rigidity and shrinking of the sclerotic, swelling of the ciliary processes, are other theories. More plausible is the ingenious and able explanation advanced by Priestly Smith, which attributes to increased lens size (that always takes place with age) a diminution or obliteration of the space between the edge of the lens and the ciliary processes, called the canal of Petit. This so-called canal is the route through which the excreted fluids of the vitreous chamber pass forward to the canal of Schlemm, and if this be blocked, the increased pressure from behind will throw the lens forward and effect the shutting off of the canal of Schlemm by the iris, as alluded to above, and which is left unexplained by others. The rarity of glaucoma in myopia, as compared with hyperopia, leads to the conclusion that the formation of posterior staphyloma may be of the nature of a relief of the pressure backward instead of the iris being pushed forward, and that in this way progressive myopia takes the place of what might otherwise result in glaucoma. But such cases are exceptional.

Varieties and Symptoms.-Glaucoma Simplex is unaccompanied by inflammatory symptoms; it may become chronic and continue with a tension only slightly above the normal for years.

In Acute Glaucoma there is a class of symptoms which is called premonitory, but how these symptoms could appear before an actual increase of pressure has taken place is for us impossible to see. These so-called premonitions are, e. g., a sudden failure of accommodative power, stronger +Sph. glasses being required for reading; fogginess of vision and colored haloes about a light are also noted. These symptoms show a premonitory

attack, which may pass off to recur at a later time. These short attacks may be numerous without being sufficiently severe to catch the patient's attention, though usually each attack leaves the eye in a worse condition. When a more severe or abiding increase of pressure sets in, it may be accompanied by vomiting and other derangements of function, tending to deceive both patient and physician. Sometimes the first noticed attack begins with fury, and in a few hours vision is wholly destroyed. This is v. Graefe's Glaucoma Fulminans. Subacute attacks are characterized by exacerbations and remissions of intensity without complete relief at any time. Absolute Glaucoma is glaucoma that has culminated in blindness. There is here no lessened tension, and the end is cataract, staphylomata, atrophy and disorganization of special organs, and of the globe itself.

Diagnosis.--The principal diagnostic sign is, of course, the characteristic feature of the disease-Increase of Tension. There is no other method of testing this but the tactus eruditus. The two index fingers are laid delicately on the closed lid, the hands supported by the other fingers on the forehead or temple, and an estimation of the tension made by soft palpation or alternate pressures. Comparison with the other eye of the patient is advisable and with normal eyes, upon which last much previous practice will only give the precision desired. T. +? is the symbol of a possibly increased tension, as Tn. means the normal, and T. + 1, T. + 2, T. + 3 indicate the varying degrees of hardness up to thể last or a stony hardness. The minus sign with the same figures means diminished degrees, T. 3, e. g., indicating a perfectly flaccid condition of the globe.

Perhaps the second in importance of the diagnostic signs, like all the others to follow, is a mere result of the abnormal tension to which the tissues were subjected; this is anæsthesia of the cornea. Direct the patient's eye upward to get the visual axis out of line, and then touch the cornea with a twist of absorbent cotton or silk, and what would otherwise cause spasmodic shrinking, etc., is hardly perceived, showing the pressure has paralyzed nervous transmission.

Amplitude of Acc. is lessened for the same reason, and again, for the same cause, there is dilatation and comparative immobility of the pupil. Cloudiness of the cornea is produced by pressure, as is readily shown in excised pigs' eyes, and there is congestion of the veins. These are the chief external signs. If the fundus oculi be visible, arterial pulsation (which is always pathological) exists upon the papilla, or is producible by the slightest pressure. The infallible indication, however, is the cupping of the papilla (Fig. 27), easily distinguishable from the " physiological

H

cup" by its extent, depth and the fore-shortening, or even disappearance, of the vessels as they climb up and over the precipitous sides of the tip. Here, instead of requiring + Sph. lenses to bring it into clear view, we have to rotate in - Sph. lenses, as the bottom of the cup lies further from us than the retina or the brim of the cup. About this brim the "glaucomatous ring" is seen in chronic simple glaucoma. Contraction of the field of vision and loss of color perception are, of course, synchronous with diminished acuity and heightened tension, and it need not be added that pres

sure upon sensory nerves produces the most exquisite pain, as also that the abnormal pressure must induce inflammatory symptoms in many parts of the eye or adjacent tissues.

Treatment.-Eserine, it is certain, has a tendency to reduce the intraocular tension, and when an iridectomy is not at the time advisable or possible, perhaps, also, always, as a tentative or preliminary proceeding, its frequent instillation should be tried before proceeding to the operation that is most widely recognized as the most effectual check, and possibly