60 



MICROSCOPY OF THE LIVING EYE 



of the reflecting surface. Suppose we see by D.I.S.R. an abnormal 

 picture of the corneal endothelial surface, such as Fig. 27, in 

 which we can say of the dark patches that they are either areas 

 which fail to give a specular reflex at all (cjp. d, d, d, Fig. 19) or 



else areas which, though 



Al 



Fig. 26. — Alteration of the axis of specular 

 reflection with varied tilt of the specular 

 surface. 



'^---^ /i D possessing reflecting pro- 



perties, fail, from altera- 

 tion of contour (cp. c, c, c, 

 Fig. 19) to reflect the 

 light along the same axis 

 as the light reflected by 

 the general endothelial 

 surface. If they are the 

 latter, glinting specular 

 reflections will be seen off 

 part of their contour if 

 they are viewed, through 

 one side of the microscoi^e, at an angle which is not that of 

 specular reflection for the whole field as seen through the other 

 side of the microscope ; consideration of the position of the 

 glinting reflections and of the tilt of the axis of observation 

 readily enables the observer to 

 interpret whether the contour 

 variations are of the nature of 

 convexities or concavities. 



To summarise, observation 

 by D.I.S.R. is no more than 

 observation by ordinary D.I. 

 of any part of an anatomical 

 optical face having mirror-like 

 properties with the added con- 

 dition that the chosen axis of the microscope focused on that 

 part shall correspond with whatever direction at the moment 

 constitutes the path of specular reflection of the illuminating 

 beam. 



A feature seen in the course of the thin optical sections of the 

 cornea and the anterior and posterior lens-cortex may here be 



Fig. 27. — Views by D.I.S.R. of a corneal 

 endothelial face in which areas of 

 altered contour either are not reflect- 

 ing along the mean axis of observa- 

 tion or are not reflecting at all. 



