736 VERHOEFF AND BELL. 



absorbed by the lens, reaching from 300 ijlix to about 400 nfx, the chief 

 absorption is, following the general theory which we have already 

 explained, at the front surface, hence if by any stretch of the imagina- 

 tion glassblowers' cataract could be assumed to be due to an indefi- 

 nitely long application of such rays it should occur at the anterior and 

 not at the posterior cortex. To rays in the ordinary visible spectrum 

 the lens is notoriously transparent and in default of absorption of 

 energy there is no reason to expect any specific effects from it. We 

 have been able by the use of sources of extreme power greatly concen- 

 trated, as our experiments show, to obtain specific action of the ultra 

 violet rays only to a microscopic depth, 20 ju, so that the experimental 

 evidence lies squarely against any lesions directly producible by such 

 sources in the posterior cortex, particularly in the absence of any effects 

 in the anterior cortex. 



This reasoning also holds for the time integrals of any effect of such 

 raj's over periods however long, for whatever the aggregate effect 

 might be it would always remain much greater at the anterior than at 

 the posterior part of the lens substance. The absorption of the media 

 of the eye for various wave lengths and especially those predominant 

 in sources of the temperature considered has been investigated by 

 Aschkinass ^ who has shown that the characteristic absorption of the 

 long waves is essentially that of water. An analysis of Aschkinass' 

 results by Luckiesh ^^° shows that for sources of moderate temperature 

 the resulting absorption is chiefly in the cornea and aqueous, that is in 

 the outer layers of the absorbing media. For a source of the tempera- 

 ture of a glass furnace, between 80 and 90% of the energy will be 

 absorbed by the cornea alone, and the amount stopped in the lens 

 from all causes would not be over 3 or 4%, but this small fraction of 

 the total is still absolutely a considerable quantity and is somewhat 

 concentrated in the lens since not less than three-fourths of the total 

 refraction of the eye is due to the cornea. There is therefore a slight 

 tendency to concentrate energy toward the rear of the lens. Such 

 concentration must be small, however, owing to the contracted pupil 

 and the resulting narrow angle of the pencil of rays entering the lens. 

 It is doubtful whether the actual concentration would reach more than 

 a few per cent and the effect of this would be more than offset by the 

 greater al)sorption in the anterior cortex. 



As regards the distribution of temperature in the eye resulting from 

 the intense radiation most of the absorption takes place as stated, in 

 the cornea, and a greater proportion in the aqueous than in the lens. 

 The front of the cornea is of course rapidly cooled by convection and 



