THE OPHTHALMOSCOPE. 



579 



the room. If, however, we look in at night, when the room is 

 lighted up while it is dark outside, we can see every object 

 clearly. So, if we illuminate the inside of the eye by any means, 

 we shall be able to see the details of the inside of the eye 

 chamber. 



This means is supplied by the ophthalmoscope, which reflects 

 the light from a lamp into the chamber of the eye so as to illu- 

 minate it completely, and when the surroundings are not too 

 bright, the fundus of the eye can be clearly seen and investi- 



Ophthalraoscopic view of fundus of eye, in which the central artery (g and c) and the 

 corresponding veins (h and d) are seen coursing through the retina from the optic disk 

 (A). 



gated. A lens is usually interposed between the eyes of the 

 observer and the observed, in order not only to illuminate but 

 also to magnify the fundus and enable the observer to see all the 

 details of the parts. With this instrument a round, whitish part 

 is seen a little to the nasal side of the axis of the eye, where the 

 nerve pierces the dark choroid coat. This is called the optic 

 disk. The fundus now, when lighted up, does not look black, 

 but is of a lurid red color, owing to the great vascularity of the 



