EFFECTS OF RADIANT ENERGY ON THE EYE. 759 



of abiotic energy required to produce a specific effect in solar erythema 

 is substantially the same as that required for mild photophthalmia. 



19. Erythropsia is not in any way connected with the exposure 

 of the eye to ultra violet radiations, but is merely a special case of 

 color fatigue, temporary and without pathological significance. 



20. Vernal catarrh and senile cataract we can find no evidence for 

 considering as due to radiations of any kind. 



21. Glass blower's cataract often charged to specific radiation, 

 ultra violet or other, we regard as certainly not due to ultra violet 

 light but probably due to the overheating of the eye as a whole 

 with consequent disturbed nutrition of the lens. 



22. Commerical illuminants we find to be entirely free of danger 

 under the ordinary conditions of their use. The abiotic radiations, 

 furnished by even the most powerful of them, are too small in amount 

 to produce danger of photophthalmia under ordinary working condi- 

 tions even when accidentally used without their globes. The glass 

 enclosing globes used with all practical commercial illuminants are 

 amply sufficient to reduce any abiotic radiations very far below the 

 danger point. 



23. Under ordinary conditions no glasses of any kind are required 

 as protection against abiotic radiations. The chief usefulness of 

 protective glasses lies not so much in their absorption of any specific 

 radiations, as in their reducing the total amount of light to a point 

 where it ceases to be psychologically disagreeable or to be incon- 

 veniently dazzling. Glasses which cut off both ends of the spectrum 

 and transmit chiefly only rays of relatively high luminosity, give the 

 maximum visibility w^ith the minimum reception of energy. For 

 protection against abiotic action in experimentation, or in the snow 

 fields, ordinary colored glasses are quite sufficient. 



24. So far as direct destruction of bacteria within the cornea or 

 any other tissues of the body is concerned, abiotic radiations possess 

 no therapeutic value. This is due to the fact that abiotic radiations 

 that are able to penetrate the tissues are more destructive to the latter 

 than to bacteria. 



