12th. =Other causes of pupillary immobility= include: (a) Permanence of a pupillary membrane, which has remained from the fœtal condition and may be recognized by oblique focal illumination and invariability of the pupil: (b) Adhesion of the iris to the capsule of the lens—complete or partial—in the latter case the adherent portion only remains fixed, while the remainder expands and contracts, giving rise to distortions and variations from the smoothly curved outline: (c) Adhesion of the iris to the back of the cornea—complete or partial—and leading to similar distortions: (d) Glaucoma in which intraocular pressure determines a permanent dilatation of the pupil and depression of the optic disc: (e) The pupil is narrowed in iritis, and is less responsive to atropia or other mydriatic: (f) Lesions of the oculo-motor nerve may paralyze the iris and fix the pupil. The first three and the fifth of these conditions may be recognized by the naked eye, alone, or with the aid of focal illumination, the fourth may require the aid of the ophthalmoscope and the sixth which cannot be reached by such methods, might in exceptional cases be betrayed by other disorders of the oculo-motor nerve (dropping of the upper eyelid, protrusion of the eyeball, squinting outward). 13th. =Coloboma= (_fenestrated iris_), and =lacerated iris= are recognizable by the naked eye in a good light, or by the aid of focal illumination. 14th. =Tension of the eyeball= (_Tonometry_). Elaborate instruments constructed for ascertaining ocular tension are of very little use in the lower animals. The simplest and most practicable method is with the two index fingers placed on the upper lid to press the eyeball downward upon the wall of the orbit using the one finger alternately with the other as if in search of fluctuation. The other fingers rest on the margin of the orbit. All normal eyes have about the same measure of tension and one can use his own eye as a means of comparison. The educated touch is essential. In increased tension, the sense of hardness and resistance, and the indisposition to become indented on pressure is present in the early stages of internal ophthalmias (iritis, choroiditis, retinitis), phlegmon of the eyeball, glaucoma, hydrophthalmos, and tumors of the bulb. Oblique Focal Illumination.