EFFECTS OF RADIANT ENERGY ON THE EYE. 735 



are especially liable to cataract. Peters ^^^ suggested that the cata- 

 ract was clue to the venous stasis in the vortex veins associated with 

 the forced expiration, analogous to the cataract produced experi- 

 mentally by tying off the vortex veins. Leber ^^^ advanced the view 

 that it was due to concentration of the aqueous resulting from evapo- 

 ration from the cornea and the loss of water from excessive perspira- 

 tion. Parsons ^^^ suggested that the cataract results from altered 

 nutrition due to overheating of the ciliary body. Cramer ^^, Stein ^*^, 

 and others believe that it is due to ultra violet light (chemical action), 

 while Vogt ^^^ regards the infra red rays as chiefly responsible. 



The great frequency with which glassblowers' cataract occurs, its 

 relatively uniform type, and the fact above all, that it occurs first in 

 the more exposed eye, show clearly enough that it is chiefly due to the 

 action of radiant energy on the eye itself. This is supported also by 

 the fact that the cheek shows a more marked area of discoloration on 

 the side of the first affected eye. The further questions whether the 

 cataract is due to the direct action of the light upon the lens, or upon 

 the eye as a whole, and whether it is due to abiotic or thermic action, 

 are not quite so easily answered. 



The character of the radiation from molten glass is well known. It 

 is that from a homogeneous body of relatively low temperature, 1200° 

 to 1400° C. It is certain that the spectrum of a non gaseous body 

 at this temperature does not include any of the so-called abiotic radia- 

 tion since the extreme limit of the spectrum of molten glass found by 

 any investigator is 320 nfx and estimates range from that to 334 /xju. 

 We have already shown that the abiotic action cannot be traced 

 beyond 305 nfj, and there is not the slightest indication from our 

 researches or any predecessors that there is reason to suspect an 

 extension of such activity to waves longer than 320 MM- Even if 

 there were, such rays would be stopped at the front of the lens by its 

 absorption and hence would be unable to affect the posterior cortex. 

 Moreover the radiation of a body at such temperature is relatively 

 very weak all through the ultra violet, the maximum, according to 

 Planck's law, for a body at 1300° C. lying far in the infra red 

 while the energy in the whole visible and ultra violet part of the 

 spectrum is less than 1% of the total. Hence to ascribe injurious 

 effects to the visible or ultra violet radiation without eliminating 

 once and for all the 99% of infra red radiation is to lose all sense 

 of proportion between cause and effect. To follow up the theory 

 of the matter a little further we have shown that the specific 

 .abiotic action is clearlv to be eliminated. Of the ravs whicii are 



