9th. =A corneal ulcer= may be similarly recognized. It is made more strikingly manifest by instilling into the lower _cul de sac_ a drop of a solution of fluorescin and rubbing it over the eye by moving the eyelids with the finger. This will stain the whole cornea. If now the excess of stain is washed away by a few drops of boric acid, the healthy part of the cornea is cleared up and the ulcer retains a bright yellowish green tint. 10th. =Opacity or Floating objects in the aqueous humor= (flocculi of lymph, pus, pigment, blood, worms) are always to be looked for. They may be detected by placing the eye in a favorable light. They may be still more clearly shown under _focal illumination_ (see below). 11th. =Changes in the iris and pupil= may also be noticed in a good light. The surface should be dark in the horse, and of the various lighter shades in the smaller animals, but in all alike clear, smooth and polished, without variation of shade in spots or patches and without bulging or irregularity at intervals. Apart from the congenital absence of pigment in whole or in part, which may be found in certain sound eyes, a total or partial change of the dark iris of the horse to a lighter red, brown or yellow shade implies congestion, inflammation, or exudation. The =corpora nigra= in the larger quadrupeds should be unbroken, smooth, rounded, projecting masses outside the free border of the upper portion of the iris. It should show a clear, polished surface like the rest of the iris. =The pupil= should be evenly oval with its long diameter transversely (horse, ruminant), circular (pig, dog, bird), or round with an elliptical outline on contracting and the long diameter vertical (cat). It should contract promptly in light and dilate as quickly in darkness. Place the patient before a window, cover one eye so as to exclude light, then cover the other eye with the hand and quickly withdraw. The pupil should be widely dilated when the hand is withdrawn and should promptly contract, and it should actively widen and narrow alternately until the proper accommodation has been secured. Any failure to show these movements implies a lesion in the brain, optic nerve, or eye which impairs or paralyzes vision, interferes with accommodation or imprisons the iris. In locomotor ataxia the pupil contracts in accommodation to distance, but not in response to light.