Page:Popular Science Monthly Volume 9.djvu/718

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The ophthalmoscope has become an instrument of incalculable value to the oculist. Many changes in the retina and interior of the eye, which are due to disease, can be observed and examined by means of the ophthalmoscope; and, in fact, the medical treatment of the eye has made an immense advance since the discovery of this instrument.

PSM V09 D718 Tolerable observation of the retina.jpg
Fig. 5.

The eyes of many animals—those of cats, for instance—exhibit a peculiar brilliancy, which is particularly remarkable in the dusk. It was formerly thought that the eyes of such animals emitted light independently, as it was also thought that light could be emitted by the human eye, under the influence of passion. This brilliancy, however, in the eyes of these animals is caused by a carpet of glittering fibres, called the tapetum, which lies behind the retina, and is a powerful reflector. In perfect darkness no light is observed in their eyes, a fact which has been established by very careful experiments; but, nevertheless, a very small amount of light is sufficient to produce the luminous appearance in them.



THE antagonism between Science and Religion has become a commonplace of literature. Both preachers and physicists have narrated with bitterness of spirit the battles which they have fought, the wrongs which they have suffered, the complaints which they have to make, the one against the other. The combative have plunged into the mêlée, and with slashing pen or tongue given it new asperity and new sources of grievance. The peaceful have endeav-