EFFECTS OF RADIANT ENERGY ON THE EYE. 767 



and finally produced the yellowish colored "Euphos glas" which 

 they recommend as very satisfactory, not only for protection glasses, 

 but also for use in making arc light coverings or mantles. 



However Birch-Hirschfeld ^* in 1907 considered the above exposure 

 so intense as to afford no criterion for cases as they usually occur. 

 From his results he asserted that one need not be afraid to use the 

 ordinary smoked, uviol, flint, or even common glass, in the great 

 majority of cases. He exposed a rabbit's eye for 1 hour as close as 

 10 cm. to a uviol lamp (mercury vapor tube) protected only by a 2 mm. 

 thickness of common glass. After the 6 hour latent period no symp- 

 toms whatever developed although the control rabbit's eyes were 

 badly damaged. Further he exposed his own eyes to a 3000 c. p. 

 quartz mercury arc lamp at 1 meter distance using smoked glass 

 goggles as a protection. Although the surrounding skin of his face 

 was burned, no symptoms of ophthalmia electrica developed. Birch- 

 Hirschfeld ^* also proved that by daily exposure of the rabbit's eye to 

 ultra violet rays a chronic inflammation of the outer eye could be 

 produced which was very similar in appearance, both grossly and his- 

 tologically, with vernal catarrh, originally considered by Schiele^^^ 

 in 1899 to be a result of exposure to the light rays of the sun. In this 

 investigation Birch-Hirschfeld exposed the rabbit's eyes for 10 min. 

 every day for 180 days at a distance of 10 cm. from the " Uviol lampe" 

 of Schott. The eye lids of the rabbits were everted during the expo- 

 sure. After passing through the usual acute ophthalmia electrica a 

 chronic inflammation was established similar to vernal catarrh, 

 but no trouble in the lens or retina was noted. 



Birch-Hirschfeld considered rays shorter than 330 /x^t to be prima- 

 rily responsible for the outer eye disturbance in this case, still rays from 

 330 ju/x to 400 /x^ or more could not be excluded as etiological factors. 

 However he agreed with Axenfeld and Ruprecht^, 1907, that these 

 factors could not entirely explain vernal catarrh. Vogt*°^ in 1912 

 thought that exacerbations at least in the disease depended on thermic 

 influences. 



The Cornea: — Absorption, Injuries. 



That the cornea might suffer severe injury in bad cases of oph- 

 thalmia electjica was early noted by Terrier ^^^ in his report of 1888. 

 In these cases a dull haziness of the cornea with perhaps a phylectenu- 

 lar condition or bleb formation was first noted. This condition could 

 either go on to ulcer formation l)y infection or to panuus formation 



