VETEKINAKY OPHTHALMOLOGY. 135 



part of the ophthalmoscope, does, being a mirror 

 pierced by a hole for observation. An ophthalmoscope 

 consists principally of two parts — a mirror and a lens, 

 and the mirror is the essential part, everything else 

 being accessory. 



" Find out the cause of this eflfect, 

 Or rather say the cause of this defect, 

 For this effect defective conxes by cause.'' 



Samlet. 



MNIS. 



