770 WALKER. 



exposure a marked swelling and hyperemia of the ciliary body, and in 

 later experiments in the same way noted small hemori'hages in the 

 iris. Gross examination showed myosis and discoloration of the iris. 

 Ogneff^^^, Terrier ^^^ and Weiss ^^ confirmed these findings. 



Birch-Hirschfeld ^^ in 1904 with the Finsen 3.5 to 4.5 amp. arc light 

 for 5-10 minutes noted iritis and cyclitis in 6-12 hours with fibrinous 

 exudate into the anterior and posterior chambers. Further experi- 

 ments in 1908 with the Schott lamp 10 min. exposures at 10 cm. daily 

 for 180 days showed practically no effect on the iris though a chronic 

 eonjunctival inflammation was produced. 



Martin ^^^ in 1912 noted, in rabbits exposed 1| to 2 hours at a dis- 

 tance of 1 in. from a Kromayer mercury vapor lamp hyperemia and 

 myosis of the iris but no exudates. Further by the hemolytic method 

 of Romer he found that the iris showed evidence of damage with inten- 

 sities above 1 hour exposure at 4 in. distance. Whether the injury to 

 the iris produced when the light is of sufficient strength is a direct 

 result of light rays or a secondary effect of the corneal and outer eye 

 injury was not made clear. 



The Lens: — Absorption; Fluorescence, as a Determinant 

 OF Visibility of ultra violet Rays; Injuries; Cataracts. 



The reports of different observers upon the absorption power of 

 the crystalline lens have varied considerably. Birch-Hirschfeld ^"^ 

 in 1909 accounted for the long list of previous variations in the following 

 manner. Aside from the personal equation or individual variation 

 in observation, there is a considerable variation in the absorptive 

 power of lenses of different animals of the same species as well as of 

 different species. His results may be tabulated thus: 



Range of 

 Average Variation in 



Animal absorption Different Animals 



Swine 330 juju 15 /z/x 



Calf 328 MM 12 mm 



Ox 385 fj.fj. 30 MM increasing with age. 



To a less extent thickness plays a part, though not so very great, 

 since 5 mm. of rabbit lens has about the same absorptive power as 

 10 mm. of ox lens, for waves less than 390 nn. The formula for the 



