A text-book of physiology for medical students and physicians . e sensation, while non-corresponding points are those whichwhen so stimulated give us two visual sensations. It is evident,from our experience, that the foveae form corresponding points orareas. When we look at any object we so move our eyes that the 366 THE SPECIAL SENSES. images of the point observed shall fall upon symmetrical parts of thetwo fovese; the lines of sight of the two eyes converge upon andmeet in the point looked at. If, while observing an object, we pressgently upon one eyeball with the end of the finger, two imag
A text-book of physiology for medical students and physicians . e sensation, while non-corresponding points are those whichwhen so stimulated give us two visual sensations. It is evident,from our experience, that the foveae form corresponding points orareas. When we look at any object we so move our eyes that the 366 THE SPECIAL SENSES. images of the point observed shall fall upon symmetrical parts of thetwo fovese; the lines of sight of the two eyes converge upon andmeet in the point looked at. If, while observing an object, we pressgently upon one eyeball with the end of the finger, two images areseen at once, and they diverge farther and farther from each otheras the pressure upon the eyeball is increased. Experiment shows,also, that, in a general way, portions of the retina symmetricallyplaced to the right side of the fovese in the two eyes are cor-responding, and the same is true for the two left halves and the twoupper and lower halves. The right half of the retina in one eye isnon-corresponding to the left half of the other retina, and vice. * 061 081 OUV Fig. 158.—Perimeter chart to show the extent of the binocular visual field (shaded area)when the eyes are fixed upon a median point in the horizontal plane. versa; and the same relation is true of the upper and lower halves,respectively. If we imagine one retina to be lifted without turningand laid over the other so that the fovea? and vertical and horizontalmeridians coincide, then the corresponding points will be superposedthroughout those portions of the retina that represent the binocularfield. This statement, however, is theoretical only; an exact pointto point correspondence has not been determined have shown, however, that the corresponding pointsin the upper halves of the retinas along the vertical mid-line donot cover each other, that is, they do not lie in the actual anatom-ical vertical meridian, but form two meridians which diverge BINOCULAR VISION. 367 symmetrically
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