EFFECTS OF RADIANT ENERGY ON THE EYE, 671 



Birch-Hirschfeld states that adhesion of the pigment epitheUum to the 

 lens occurred after fixation in some of his experiments, although the 

 light intensities used were far less than those used by us. As already 

 pointed out, the adhesions noted by Birch-Hirschfeld were undoubtedly 

 artefacts due to the action of the fixing fluid alone, since they occur 

 in the case of normal eyes. In view of the numerous control eyes ex- 

 amined by this observer, it is difficult to understand why he was not 

 aware of this fact. 



The Character of the Changes Produced in the Lens by Abiotic 



Radiations. 



The light intensities and wa\'e lengths necessary for the production 

 of abiotic effects in the lens epithelium have already been given 

 (page 651). 



In none of our experiments was an opacity of the lens produced 

 sufficient to be visible through the cornea. Even when the lens was 

 examined in air after its removal from the eye it appeared perfectly 

 clear. If, however, it was placed in normal salt solution it showed 

 a delicate haziness in the pupillary area 48 hours after a severe 

 exposure. 



Histological. In all except one experiment upon the lens, the cap- 

 sule was removed and examined as a flat preparation, so that it was 

 impossible to make a satisfactory examination of the lens substance. 

 To determine the effect of the abiotic radiations upon the latter, 

 the lens in one experiment (Exp. 67) was fixed in formalin and hori- 

 zontal sections made of it. The magnetite arc, water cell and system 

 of quartz lenses were used without a screen, and the exposure was 

 20 minutes. This was the exposure that had been found to produce 

 extreme changes in the capsular epithelium. The eye was enucleated 

 at the end of 48 hours. On microscope examination the lens capsule 

 proper is found unaltered, while the epithelium shows the marked 

 changes described below. The lens substance is definitely affected 

 but only for a microscopic depth, the distance beneath the capsule 

 by actual measurement nowhere exceeding 20 fi. In this narrow 

 zone it stains much more intensely in eosin than the rest of the lens 

 substance and is highly vacuolated. Occasionally it contains an epi- 

 thelial cell which has evidently been forced into it. 



Lens Capsular Epithelium. This is the best possible tissue in which 

 to study the cell changes produced by abiotic radiations because of 



