780 WALKER. 



injuries. Temperature, therefore, they thought not nearly so much 

 to blame as the ultra violet rays from 400 nn to 350 /x/^ which fluoresce 

 the lens most strongly. The absence of rays below 320 nn accounted 

 for the absence of outer eye trouble, in answer to the question raised 

 by Birch-Hirschfeld during the previous year. In comparing the 

 cataracts of glass blowers and those produced artificially by the arc 

 light, they noted as has Widmark*^^, Hess ^^^, Cramer ^^ and others, 

 as well as Stein ^*^ later, that they both begin in the pupillary region, 

 but that while the artificially produced cataracts begin usually on the 

 anterior pole, the glass maker's cataract starts usually on the poste- 

 rior pole. For the posterior polar variety no better explanation could 

 be offered at that time than that of Cramer ^^, who believed them to be 

 the result of the greater concentration of chemical rays at that point 

 due to the refractive power of the eye media anterior to that point. 

 Other theories were concentration of the chamber fluids (Leber ^^^) 

 and increased venous stasis (Peters ^^^). However Snell^*^ in Eng- 

 land fovmd cataract no more common among glass blowers than among 

 other laliorers, and Robinson ^^^ foimd the percentage increasing aljove 

 normal only among the finishers working with very heavy metal 

 glasses, after long service. 



In 1909, Handmann^'''^ submitted an extensive statistical study of 

 senile cataracts. Hirschberg confirmed by Schulek ^^° had first sug- 

 gested the intense simlight as a factor, in the country and India, 

 and had noted the early appearance in the lower quadrant. Hand man 

 was able to prove that the senile cataract particularly of India for 

 the most part 81% (previously given by Greene ^^^ as 95%), begins 

 in the lower quadrant of the lens. This region of the lens was found 

 to be more deeply yellow colored, and therefore had a higher absorp- 

 tive power for ultra violet. The ultra violet content of light coming 

 from the sky at such an angle as to strike this quadrant is far greater 

 than that reflected into the eye from the broken surfaces below, thus 

 supporting the original idea of Schwitzer ^^^ that abiotic rays were an 

 etiological factor. Presumptive evidence at least was furnished to 

 explain the senile cataract. Schanz and Stockhausen ^^^ at once ac- 

 cepted these findings as giving the key to the etiology of a large group 

 of senile cataracts. But Birch-Hirschfeld^^ pointed out that dwellers 

 in mountainous and snowy regions of high ultra violet content were 

 not prone to cataract and considered that the shorter visible rays 

 could not be excluded here as in other cases, and Hess^^* from a 

 mathematical standpoint considered that rays not obstructed by the 

 lids and eyelashes could not reach the lower quadrant of the lens in 

 sufficient quantity to account for the condition. 



