Inhaltsangabe
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1898. Excerpt: ... THE EYE AND THE PHYSIOLOGY OF VISION. That the eye is the seat of vision is a bit of knowledge as old possibly as humanity, but it was not until 1602, when Kepler compared the human eye with the camera obscura, that any considerable attempt was made in the explanation of its function. Some time previous Porta had invented the camera obscura, and so it was but a natural step for Kepler to make this the basis for his explanation of the eye. Kepler's explanation was practically nothing more than merely the statement of such an analogy and did not deal with specific details. A few years later, 1609, the Jesuit priest Scheiner noted the inversion of the image on the retina, and made the further important discovery that the pupil contracted or expanded with the varying accommodation of the eye. In 1695 the optician Huyghens constructed an artificial eye and demonstrated on the same the action of spectacles. During the next century nothing seemed to be added to the knowledge of the eye. In 1801 Young (the founder of the present Young-Helmholtz Theory of Vision) noted and explained astigmatism. Long-sight and short-sight had been previously observed, and Huyghens had actually explained the action of spectacles in remedying these defects. Up to the beginning of this century, and even later, nothing was known of the manner in which the eye was accommodated for far and near. The necessity for such a power of accommodation had been noted by Kepler, and Descartes had actually suggested the thought that the power of accommodation resulted from the ability of the lens to change its form, but it was not until 1801 that Young demonstrated this change in experiments on his own 34 (529) eyes. Objectively this change in the form of the lens was demonstrated by the reflection...
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