. The ophthalmoscope : its mode of application explained, and its value shown, in the exploration of internal diseases affecting the eye. ifwe viewed it through the more modern astronomical telescope. 8 THE OPHTHALMOSCOPE. Ruetes illustrations are very characteristic, well-markedchanges of structure; a few drawings from his Atlas arereproduced in my frontispiece. The ophthalmoscope I make use of is a small circularmirror, indeed nothing more than the silvered mirror made foran ordinary microscope, having a hole bored in its centre, andmounted in a piece of tortoiseshell.* This form of instrume
. The ophthalmoscope : its mode of application explained, and its value shown, in the exploration of internal diseases affecting the eye. ifwe viewed it through the more modern astronomical telescope. 8 THE OPHTHALMOSCOPE. Ruetes illustrations are very characteristic, well-markedchanges of structure; a few drawings from his Atlas arereproduced in my frontispiece. The ophthalmoscope I make use of is a small circularmirror, indeed nothing more than the silvered mirror made foran ordinary microscope, having a hole bored in its centre, andmounted in a piece of tortoiseshell.* This form of instrumentis generally known as that of M. Anagnostakis, I have alsotried the plane perforated mirror of M. Coccius, M. Jaeger, anda small portable instrument, so contrived, with the lamp fixedin position, as to be always ready for use; but I give prefer-ence to the simplest form, finding it infinitely more conve-nient to hold a small instrument in my hand, which I canbring near to my patient, and turn about in any direction, asnecessity may dictate. The mode of using the instrument isshown in the annexed diagram (Fig 1). The rays from the. * This ophthalmoscope may be purchased at Bakers, 244,Holborn: Mathewss, Portugal Street; and Weedons, HartStreet, Bloomsbury. THE OPHTHALMOSCOPE. 9 flame of the lamp, reflected by the concave mirror, A B, fallin a state of convergence on a convex lens, C, in front of theeye under examination. The rays of light are so muchconverged by the additional refraction they undergo on enter-ing the eye, that they quickly come to a focus, cross, and aredispersed over the retina, and thus this membrane is fullyilluminated. The observers eye at D is looking through thesmall central aperture in the middle of the concave mirror,which he holds in his hand. In the examination of most eyes,we find it necessary to use a bi-convex lens, C, of about one-and-a-half inch focus. The rays coming from the lamp areinverted as they quit the concave mirror—an inverted imageo
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