There are other tests, but these are not satisfactory; such as covering the eye with the hand or a hat. The hand is semi-transparent, and so can only induce partial darkness; the hat does not fit the inequalities of the horse's countenance, therefore it is useless. Of the same nature is aiming pretended blows at, or moving the hand before, the suspected eye. The other senses, by constant exercise, become so very acute during loss of sight, that winking is no proof of vision: the lid may move, and, nevertheless, the horse be stone blind. [Illustration: THE BASE OF THE BRAIN. _a._ The point of junction between the right and left optic nerves. _b b._ The healthy optic nerve, of a white color, originating on the left side and proceeding to the left eye. _c c._ The paralyzed or unhealthy optic nerve, diminished in size and darker in color. It ran to the right eye; but its diseased condition can be clearly traced to originate from the left side of the brain.] Nothing can be done for paralysis of the optic nerve. The injury once established, its effects are lasting. Butchers and other people, who foolishly pride themselves upon their fast trotting steeds, and whose natures are not unpleasantly susceptible, often induce the affection. It lessens the value of the horse, dooms it to a lower class of proprietors, and takes from the creature's life much of the pleasure which otherwise might lighten the animal's existence. After death, an anatomical peculiarity is observed. The optic nerves, subsequent to leaving the brain, unite and exchange fibers. Neither nerve pursues an absolute course; yet, consequent on decease, if the right eye were blind from gutta serena, the left nerve, or the nerve originating from the left side of the brain, alone is affected: the disease seems confined to that part. The opposite nerve is perfectly white and healthy; but the one affected with paralysis is of a yellowish color, softer nature, and sensibly diminished in bulk. So, if blindness afflict both eyes, both optic nerves are then of diminished size and of a yellowish hue. CHAPTER II. THE EYES--THEIR ACCIDENTS AND THEIR DISEASES. SIMPLE OPHTHALMIA. [Illustration: SOME OF THE RESULTS OF IMPERFECT VISION.]