EFFECTS OF RADIANT ENERGY ON THE EYE. 761 



rescence of the crystalline lens, of various solutions and of the retina. 

 The fluorescence of the latter he discovered in the morbid state with 

 Setschenow. A number of observers, Eisenlohr ^°^ in 1856, Janssen ^^^ 

 in 1860, Franz ^^i in 1862, Listing 228 in 1865, Mascart 2*° in 1869, 

 Sekulic ^^* in 1872 and Sauer ^°^ in 1875 continued the study of the 

 same question of the length of the visible spectrum in much the same 

 manner. Their results, with the exception of those of Eisenlohr and 

 Sauer, added little however, since, as the latter pointed out they 

 were not free from certain objections which will be taken up more 

 in detail under the discussion of the properties of the lens. 



As early as 1858, Charcot ^^ gave the first description of photoph- 

 thalmia and erythema produced by a small electric laboratory furnace 

 (cf. page 635). 



In 1867 Czerny ^^ made the first experimental observations on the 

 effect of direct sunlight on the retina. Even through heat filters 

 he found he could produce in the rabbit's eye marked destruction of 

 retinal elements in 10 to 15 seconds exposure with concentrated sun 

 rays. Deutschman ^^ later (1882) showed that these changes could be 

 noted in 1 second in the same manner. Herzog ^"^^ confirmed these 

 results in 1898 and reduced the exposure time to § sees. In some 

 of these cases there wei'e cataractous lens changes but no outer eye 

 disturbance. 



TyndaH ^^° in 1876, made an important contribution to the subject 

 in establishing the fact that ultra\iolet rays are absorbed by the 

 atmosphere, since the ultra violet content of the solar spectrum was 

 found to be much greater on high mountains than on low plains. 



In 1806 *^^ Wenzel and later von Beer in 1817 ^^^ pointed out the 

 disposition to cataract among glass blowers. 



The introduction of the arc light in 1879 and 1880 mark an epoch 

 in the history of this subject, for at least two reasons; first, because a 

 means was afforded for far more accurate and extensive study of ultra 

 violet light which the electric arc so abundantly supplies; secondly 

 because immediately after the use of the electric arc for lighting 

 and high temperature furnaces became general, cases of what was 

 later designated as ophthalmia electrica, began to make their appear- 

 ance. Martin 2^7 and Nodier 2^8 in 1881 reported on these cases, and 

 although they correctly described the symptom complex, their expla- 

 nation of the phenomenon as a sympathetic reflex from the injured 

 retina was soon proved to be incorrect. 



In 1882 Leber 221 after studying the cases of cataract formation 

 after exposure to lightning came to the conclusion that such cataracts 

 were produced electro-chemically. 



