Hemorrhages occurring under the conjunctiva (or membrane lining the inner surface of the lids and covering the front surface of the eyeball) may be caused by blows or other injury to the eye, by violent coughing, by straining, etc. Dark-red spots may appear in the white of the eyeball, slightly raised above the surface, which are little blood clots under the conjunctival membrane. No special trouble results and there is nothing to be done except to wait till the blood is absorbed, which will happen in time. If the eyes water, solution of zinc sulphate (one grain to the ounce of water) may be dropped into the eye, twice daily. Hot applications are beneficial here to promote absorption of the clot. =EYE-STRAIN.=--Eye-strain is commonly due to either astigmatism, nearsightedness, farsightedness, or weakness of the eye muscles. The farsighted eye is one in which parallel rays entering the eye, as from a distance, come to a focus behind the retina. The retina is the sensitive area for receiving light impressions in the back of the eyeball. Sight is really a brain function; one sees with the brain, since the optic nerve endings in the back of the eye merely carry light impressions to the brain where they are properly interpreted. In order that vision be clear and perfect, it is essential that the rays of light entering the eye be bent so that they strike the retina as a single point. In the farsighted or hyperopic eye, the eyeball is usually too short for the rays to be properly focused on the sensitive nerve area in the back of the eye. This defect in vision is, however, overcome by the act of "accommodation." There is a beautiful transparent, double-convex body, about one-third of an inch thick, which looks very much like an ordinary glass lens, and is situated in the eye just back of the pupil. This is what is known as the crystalline lens, and the rays of light are bent in passing through it so as to be properly focused on the retina. The foregoing statements have been made as though objects were always at a distance from the eye, so that the rays of light coming from them were almost parallel. Yet when one is looking at an object within a few inches of the eye the rays diverge or spread out, and these the normal eye (if rigid) could not focus on the retina--much less the farsighted eye. But the eye is adaptable to change of focus through the action of a certain muscle, situated within the eyeball about the lens, which controls to a considerable extent the shape of the lens. When the muscle contracts it allows the lens to bulge forward by virtue of its elasticity, and, therefore, become more convex. This is what happens when one looks at near objects, the increased convexity of the lens bending the rays of light so that they will focus as a point on the retina. (See Plate I, p. 30.)