LENS-INJURY AND VITREOUS 85 



concussion-injury to the eye produces at the time a scarcely detect- 

 able inlluence on what is presumably the most vulnerable part of 

 the lens, viz., the newest formed subcapsular fibres. As the years 

 go by this particular layer migrates deeper and deeper, and though 

 in mild cases its transparency is not diminished and it is therefore 

 invisible by any form of retroillumination, it has been optically 

 modified permanently in some way so that it scatters the light,- 

 appearing in the thin optical section as a clear relucent curved 

 line nearly concentric with the lens capsule from which it has 

 become separated. In other words, concussion injury to the eye 

 can permanently affect a very thin layer, giving it increased 

 relucency, detectable by no other means than direct illumination 

 in a slit-lamp optical section ; and the level of the zone, i.e., its 

 depth from the capsule, affords a very precise indication of the 

 relative time that has elapsed since the receipt of the blow which 

 caused it (15). The condition is not illustrated here ; its 

 appearance is not unlike, but very much fainter than, that of 

 the thin curved lines in the cortex of Fig. 50, C, with the 

 omission of the coarser, thicker regions of change drawn there. 



The normal vitreous fluid shows a gossamer-like fibrillar or 

 reticular optical appearance whose constituents sway and oscillate 

 with movement of the eye. This appearance is usually absent for 

 a short distance immediately behind the posterior lens-capsule, 

 the retrolental region being a relatively non-relucent space which 

 presumably contains aqueous fluid (see R, Fig. 1). In some inflam- 

 matory conditions of the interior of the eye this fibrillar mesh- 

 work gains definite adhesion to the face of the posterior lens- 

 capsule. Inflammatory and degenerative products may appear 

 in the vitreous, sometimes in gross form, e.g., ball-like masses of 

 cholesterin crystals. If these are examined in the slit-beam with 

 low ocular magnification they appear somewhat as in Fig. 51, A ; 

 but if high magnification in used they appear somewhat as in B, 

 a false impression of exaggerated size tending to be conveyed by 

 those of the illuminated clumps which are not in the immediate 

 focal plane of the microscope, which in this drawing is supposed 

 to be just immediately behind the posterior lens-capsule. 



The illustrations which are the subject of this article have been 



