762 WALKER. 



In 1883 de Chardonnet ^^ used the ultra violet rays from the arc 

 light to study the absorption power of various parts of the eye, and 

 emphasized for the first time the very important role of the lens 

 as a determinant for the limit of visibility of the short waves of the 

 spectrum, by virtue of having the highest absorption power of all the 

 eye parts. He argued therefore that aphakic eyes should have a 

 greater range of spectral vision than normal eyes. Accordingly 

 he examined two patients who had clear eye media after the extraction 

 of cataractous lenses. He asked these patients to observe an arc light 

 through a quartz glass plate, thinly silvered so as to cut out all rays 

 except those between 343 /x/u and 301 mm hues. Normal eyes could not 

 make out on looking through this glass whether the arc light was 

 burning or not, but the aphakic patients could even detect motion of 

 the light. 



In 1886 Meyhofer ^*^ found 11.6% of glass blowers under 40 years of 

 age had cataracts, and these were mostly left sided where heat exposure 

 was greatest. 



In 1888 Hess ^^^ allowed an electric spark to impinge on the supra- 

 orbital region of a rabbit and produced equatorial cataracts. There 

 was more or less central distruction of lens capsule and vacuolization 

 of anterior lens fibres with peripheral increase of mitotic figures in 

 the capsule. This result was later confirmed by Chiribuchi, but was 

 shown to be an electrochemical rather than abiotic effect. 



It remained for Widmark *^^ in 1889 to experiment with the effect 

 of ultra violet light on the eyes of the laboratory animals. He repro- 

 duced the stages of electric ophthalmia in the rabbits' eyes and con- 

 sidered the reaction to be of the nature of an inflammatory erythema. 

 He first demonstrated the protective power of the lens by interposing 

 a fresh rabbit's lens in the path of the ultra violet rays to which the 

 rabbit's eye was exposed. The rabbit's eye in this case failed to give 

 the characteristic reaction. 



Hirschberg ^''^ in 1898 first suggested the possible influence of intense 

 sunlight in producing early senile cataracts in India and in the country, 

 though Schulek^^^ had in 1895 from the statistics of Grosz, already 

 noted that the senile cataract was more common in people working 

 on the hot plains than in city dwellers. Schwitzer^^^ was the first 

 to incriminate the ultra violet portion of the sunlight as an etiological 

 factor in these cases. Hirschberg ^^* in 1901 first noted that the 

 senile cataract almost always began in the lower c^uadrant of the lens. 

 Perhaps stimulated by the possibilities of protection to the eyes sug- 

 gested by Widmark's experiments, Schuleks^*^ in 1900, examined a 



