1912.] The Effects of Ultra- Violet Hays upon the Eye. 



325 



effect even on the conjunctiva after exposures of 1 hour at 5 inches daily 

 for 2 weeks 



B. Repeated Exposures of Moderate Intensity. 



In this series no speculum was employed and the intensity was below 

 that necessary to cause immediate damage to the anterior capsule, as deter- 

 mined by preliminary single exposures. 



Thirteen rabbits (of which 3 were albinos) and 3 guinea-pigs have been 

 exposed at distances of 4 inches to 3 feet over periods varying from 

 2£- to 12 months. All were young animals at the commencement, and in 

 each case the left eye was exposed, the right being used as control. 



They may be grouped into three classes according to the degree of exposure 

 and the severity of the inflammatory reaction which follows, the depth of 

 corneal opacity being the most useful criterion of the latter. 



Results. 



Class I: No Corneal Opacity . — In this group 5 rabbits and 3 guinea-pigs 

 were exposed for from 1 to 3 hours weekly at 3 feet for 3 to 9 months. 

 They were killed 1, 2, 3, and 4 days after the last exposure. In each case 

 there was slight chronic conjunctivitis, the media were clear, and the anterior 

 lens capsule was normal on microscopical examination. 



Glass II: Slight Corneal Opacity. — Four rabbits were exposed for 1 hour 

 every 10 days at 4 inches for 3, 7, 10, and 12 months respectively. They were 

 killed 4, 7, 7, and 13 days after the last exposure. In each case there was 

 marked chronic conjunctivitis with thickening of the lids and slight ectropion. 

 There was moderate corneal and no lenticular opacity. In Eabbit No. 3, 

 exposed for 12 months, there was a ring-shaped zone of cell proliferation in 

 the pupillary area of the anterior lens capsule (see Plates 6 and 7). The latter 

 was normal in the other three animals. 



Class III : Dense Corneal Opacity. — Four rabbits were exposed for 3 hours 

 every 2 weeks at 4 inches for 3, 9, 10, and 11 months respectively. In each 

 case there was chronic conjunctivitis with marked ectropion. The cornea 

 showed a dense opacity which had undergone vascularisation. The lens was 

 clear, and the anterior capsule normal. The animals were killed 1, 2, 7, 

 and 10 days after the last exposure. 



With one exception, therefore, this series shows no change in the lens or 

 its capsule as the result of long-continued exposure to rays of short wave- 

 length. With regard to this exception two possible explanations may be 

 advanced. 



1. It is an example of a condition described by Hess (Eef. 10). In 1907 



