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A TEXTBOOK OF PHYSIOLOGY 



him to receive light reflected from the retina of the subject, and thus 

 actually to see the illuminated retina. The instrument consists of 



FIG. 369. OPHTHALMOSCOPES. 



& mirror with a central aperture so arranged as to reflect light from 

 some source through the pupil into the interior of the eye. The 



FIG. 370. EXAMINATION OF THK EVE OF A FROG BY MEANS OF 

 MIRROR (DIRECT METHOD). 



observer, looking through the central aperture, is able to view 

 illuminated posterior wall of the eye. 



