SPECULARLY REFLFXTING SURFACES 



53 



are seen in Fig. 49, A. If the apparent flattening of the anterior 

 corneal face, in Fig. 18, A, were a true flattening, it would prob- 

 ably produce an optical distortion of the deep face of the block, 

 such as is sometimes quite difficult to distinguisli from real dis- 

 tortion. An inexperienced observer studying with high power the 

 deep face of the cornea can be misled into describing supposed 

 pathological features which are no more than optical illusions 

 produced by shadow effects cast by true change of this superficial 

 face (see Fig. 45, A). 



The examination, bv direct illumination, of the fluid inter- 



Fig. 19. — Reflection from a polished surface whose specular 

 qualities are impaired at d, d, d, and whose contour is 

 altered at c, c, c. 



spaces — the anterior and the vitreous chambers — will be referred 

 to later. 



Another aspect of direct illumination must now be referred to ; 

 it concerns the study of the four highly smooth specularly reflect- 

 ing surfaces — the two corneal and the two lental. Everyone is 

 familiar with the ordinary means resorted to of looking for pat- 

 terning or graining on a polished or semi-polished surface, viz., so 

 to dispose the area observed that it constitutes a reflecting surface 

 from some source of light to the observer's eye ; thus may be 

 seen the graining of certain finished surfaces of leather — when the 

 graining is due to truly superficial irregularities — or superficial 

 scratches on a polished wood or metal surface. It is well to consider 

 the simple manner in which these features are thus revealed. In 



