EFFECTS OF RADIANT ENERGY ON THE EYE. 763 



great number of substances for protective properties. Unfortunately 

 the substances he found to have the necessary transparency and ab- 

 sorptive power were certain liquid solutions. His results for the 

 absorptive power of the lens and the other parts of the eye were the 

 same as those obtained by de Chardonnet. The study of protective 

 glasses was later taken up by Staerkle^*^. and Vogt^^^, and quite 

 recently with more success by Hallauer ^^**'^^^, Schanz and Stock- 

 hausen^^^, and Birch-Hirschfeld^^ 



Widmark ^^^ in 1901 and 1902 continued to develop the experimental 

 method of studying the problem on the eyes of laboratory animals. 

 He introduced some very ingenious experimental arrangements and 

 was the first to show with the aid of the microscope that ultra violet 

 rays can produce definite pathological lesions of the corneal and lens 

 epithelium as well as of the conjunctiva and the skin of the lids and 

 face. Further he believed he had ascertained that the injuries to the 

 lens can be readily aggravated until cataract formation is the result. 

 He found that heavy glass (18 mm. thick) when interposed prevented 

 these changes. Solutions of quinine sulphate were equally protective. 

 He was the first to note the similarity of ophthalmia electrica and the 

 outer eye trouble in snow-blinding. 



It was not till 1907 that these results received some confirmation 

 by Hess ^^^. A number of observers had looked for lens changes both 

 before and afterwards without success, or with variable results. Thus 

 Ogneff 2^^ in 1896 using an arc light of .5000 to 8000 c. p. noticed no 

 lens trouble but much outer eye trouble as Widmark *^^ had shown 

 in 1889. Herzog ^^^ in 1898 repeated this work with a heat filter and 

 a common glass optical system on young rabbits and considered that 

 any small effect such as he found was due to heat transformation. 

 Birch-Hirschfeld ^° in 1904-5 found no lens changes with 4-10 min. 

 exposure to a 4 amp. Finsen light. HerteP^° in 1903 using the 

 magnesium spark likewise noted no lens change; nor did Strebel 

 using 5 min. exposures to a 6 amp. iron arc light. 



Hertel's -^^^ work in 1903 was based on his idea that the pathogenic 

 range of ultraviolet rays should be determined on the living cell 

 rather than on the photographic plate since there was a difference 

 in the action of these rays on chemical and living substance. He 

 therefore enclosed certain bacilli, in tiny quartz glass boxes which 

 could be inserted into the aqueous or vitreous chambers of the eye. 

 Exposing the eye, then, to the ultra violet rays from a magnesium 

 electrode spark, he found that waves of 280 mm would not pass through 

 the lens and kill the organisms (B. Coli) behind it even after 60 min. 



