68 



Messrs. H. Hartridge and A. V. Hill. 



100% 



50%- 



0% 



5,000 A.U 



2^.000 



of water between. In this way the loss of light at the surfaces of the trough 

 was allowed for. Water of several thicknesses was measured in order to give 

 suitable values from which to calculate the absorption by thin or thick layers 

 of eye media. From these measurements we then calculated the absorption 

 by the different structures of the eye, using the values given in Table V 

 for their thickness and the percentage of water contained in them. 



Table V. 



Structure. 



Thickness. 



Refractive 

 index. 



Water. 



Equivalent thick- 

 ness of water. 









per cent. 







1 -15 



1 -377 



90 



1 -04 



Aqueous humour 



2 -4 



1 -335 



99 



2-38 









84 







4-05 



1 39 



92 



3 -55 



Vitreous humour 



15 



1 -34 



96 



14 -4 



(The values in the last column were calculated by multiplying the thickness of the structure by 

 the percentage of water contained by it.) 



