SPECULAR IMAGES 



57 



scope (Fig. 22, pc') is in focus on that patch (Fio-. 22, pc). If 

 the microscope (X') is in visual focus on the level X, then the 

 picture seen will be that of B (Fig. 21). If the microscope (d' or 

 p'. Fig. 22) is in visual focus on the levels d or p, the picture seen 

 will be something like C (Fig. 21) ; in Fig. 21, B and C are merely 

 optical effects seen along the axis a' (Fig. 22), and only the pre- 

 cise conditions which 

 create and render 

 visible the view A 

 (Fig. 21) will allow the 

 observer to study the 

 area of the lens- 

 capsule (pc, Fig. 22) 

 by D.I.S.R. It is of 

 more than theoretical 

 importance to grasp 

 the significance of 

 these images, because 

 it is frequently not at 

 all easy for the ob- 

 server to know at 

 what level his micro- 

 scope is focused when 

 he^ is searching about 

 to view an area bv 

 D.I.S.R., and a know- 

 ledge of the level of 

 the mirror-image will 

 always help him to 

 find the level of the area creating that image. Similar principles 

 apply to the study of the anterior corneal mirror-surface and 

 its image. 



When we come to observation of the deep, i.e., endothelial, 

 face of the cornea by D.I.S.R. (Fig. 24), the area seen thus has a 

 fairly bright golden lustre, though it is relatively much duller than 

 that of the vividly reflecting epithelial surface ; and it is beautifully 

 carpeted by a minutely patterned mosaic representing the outline 



Fig. 22. — Observation along the axis of the 

 specularly reflected beam from the posterior 

 lens-capsule. 



