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Optic Nerve and Retina. In the acute form the retina and optic nerve present the same condition that is present in the vascular tunic; namely, that of venous stasis with the consequent edema. Frequently minute hemorrhages occur in the retina, particularly in violent acute attacks. Cupping of the discs slowly develops, causing more or less stretching of the nerve fibers over the edge of the cup.
The back of the iris is lined with dark pigment, and as the coloring matter is more or less abundant, we may have a variety of colors. This pigment layer and that of the choroid and retina absorb the light entering the eye, so that little is reflected. The pupil appears black, just as the open doorway to a dark closet seems black.
Now as Sir Isaac Newton has shewn, that all the different colours are reflected or transmitted by the laminæ of soap bubbles, or of air, according to their different thickness or thinness, is it not probable, that the effect of the activity of the retina may be to alter its thickness or thinness, so as better to adapt it to reflect or transmit the colours which stimulate it into action?
It was to be famous, a national character, whose picture was printed on the retina of the million. Never had Jones felt more inclined to stick to his position than now, with the hounds on his traces, a tramp for his companion, and darkness ahead. He felt that if he could once get to London, once lay his hands on that eight thousand pounds lying in the National Provincial Bank, he could fight.
Motions of hands, wavings and gestures, rudely convey the framework, but the finish is not there. To-day, and day after day, fresh pictures are coloured instantaneously in the retina as bright and perfect in detail and hue. This very power is often, I think, the cause of pain to me. To see so clearly is to value so highly and to feel too deeply.
By repeated groping about and touching, the child knows by experience that his hand retains the same form and extension through all the variations of distance and position under which it is observed, notwithstanding that the form and extension of the image on the retina constantly change with the different position and distance of his hand in respect to his eye.
I went and stared at nothing in my shaving-glass, at nothing save where an attenuated pigment still remained behind the retina of my eyes, fainter than mist. I had to hang on to the table and press my forehead against the glass. "It was only by a frantic effort of will that I dragged myself back to the apparatus and completed the process.
Miss Grace Winthrop, having contrived for herself, with the intelligent assistance of the porter, a most comfortable nest of pillows, suffered her novel to remain forgotten upon her knees; and, as she leaned her pretty blond head against the wood-work separating her section from that adjoining it, looked out upon the brown mountains, and accorded to those largely-grand objects of nature the rare privilege of being reflected upon the retina of her very blue eyes.
This was the first time she had yet shown any tendency, so far as I had seen, to be interested in anything, or to talk to me. I seized the occasion, and gave her, as well as I could, the sad and pretty picture that remained, and always will, in the vacant air, when I think of her, on the mysterious retina of memory.
The gentle stimulus of the light proceeding from the grain that affects the retina of the chicken, gives occasion for the reproduction of a many-linked chain of sensations, perceptions, and emotions, which were never yet brought together in the case of the individual before us.
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