62 



MICROSCOPY OF THE LIVING EYE 



B 



Fig. 30. 





Fig. 31. 



Figs. 30 and 31. — Specular lustre in the 

 lens-cortex seen in thin optical section. 



the axes of illumination 

 and observation make 

 equal angles with the 

 normal. 



The term " Proximal 

 Illumination " (P.I.) (10) 

 is an appropriate one to 

 apply to the displaying 

 of features below the sur- 

 face, and within the sub- 

 stance, of tissues which 

 are translucent, but not 

 transparent, in the way 

 indicated in Fig. 32. In 

 the anterior half of the 

 normal eye this applies to 

 the sclera, with its over- 

 lying tissue, and the iris ; 

 and in pathological eyes 

 mainly to " opaque " 

 lenses and to areas of 

 inflammatory exudates. 

 Under the conditions of 

 Fig. 32, if the iris be one 

 whose stroma is not deeply 

 pigmented its dark sphincter 

 muscle, lying near the pupil, 

 may often be seen when the 

 beam is focused not on the 

 sphincter, but into the stroma 

 in the immediate proximity ; 

 similarlv the blood vessels are 

 often thus easily seen deep 

 within a semi-opaque tissue. 



A method of detecting 

 abnormalities of or on the 

 cornea — already referred to 



