666 VERHOEFF AND BELL. 



The Histological Changes Produced in the Cornea by Abiotic 

 Waves over 295 mm in Length. 



Since, for reasons already given, the central portion of the cornea 

 under the usual conditions of the experiments is much more strongly 

 affected than the periphery, the various degrees of injury produced 

 are easily made out by examining the cornea from the periphery 

 towards the centre. Examined in this way twenty-four to forty-eight 

 hours after exposure, it is found that the epithelium first shows spacing 

 out of its basal cells, and then in addition descjuamation of the super- 

 ficial layers until finally the epithelium is more or less abruptly cast off. 

 At the margins of this erosion the individual epithelium cells show 

 changes similar to those met with in the case of the lens capsule, that 

 is, formation within the cytoplasm of eosinophilic and basophilic 

 granules. Swelling of the cells, however, is not noticeable, possibly 

 because the cells are cast off when this occurs. The nuclei are rela- 

 tively little affected, although some of them are pycknotic. Mitotic 

 figures are observed only in the apparently normal epithelium at the 

 periphery of the cornea. 



After exposures through a crown screen (295 fxix) sufficient to produce 

 injury to the lens capsular epithelium, the corneal lamellae show slight 

 if any changes; possibly they stain less deeply in eosin. The corneal 

 corpuscles, however, show marked changes. Just as in case of the 

 lens epithelium, all of the cells are not equally injured and certain 

 cells here and there entirely escape, which are fewer in number the 

 more severe the exposure. In the most exposed region, after twenty- 

 four hours many of the nuclei are barely or not at all visible, while 

 most of the others are in various stages of pycknosis and fragmen- 

 tation. The cytoplasm often contains eosinphilic and basophilic 

 granules similar to those seen in the lens epitheliimi. These are more 

 abundant after twenty-four hours and are best seen in thin tangential 

 sections. The eosinophilic granules are less readily seen in the cornea 

 than in the lens epitheliimi, probably because they are to a greater 

 or less degree masked by the eosin stained stroma. The effect on the 

 corneal corpuscles is progressively less the deeper they lie, but an 

 exposure of five minutes to the double lens system through the crown 

 screen (295 /i/x) is sufficient completely to destroy all the corpuscles 

 in the entire thickness of the cornea and also to destroy the endo- 

 thelium. Polymorphonuclear leucocytes begin to invade the cornea 

 in about twenty-four hours, reaching their maximum number in about 



