668 VERHOEFF AND BELL. 



therefore that the effect is due ahiiost entirely to waves shorter than 

 295 /i/i. After an exposure of four minutes to the bare magnetite 

 arc, at a distance of 20 cm. the epithehum, at the end of forty-eight 

 hours, is entirely lost from the central two-thirds of the cornea. 

 At the periphery the epithelium shows gradually increasing desquama- 

 tion of its cells until it is reduced to a single layer for a variable distance 

 and then abruptly ends. The cells even in the single layer are appar- 

 ently not severely injured, and occasionally one is found in mitosis. 

 They do not contain basophilic and eosinophilic granules, probably 

 due to the fact that the shortest waves were absorbed by the super- 

 ficial cells, while the remaining waves were not sufficiently intense 

 at the periphery of the cornea to injure the deeper cells. The corneal 

 corpuscles, lamellae, and endothelium are normal. There is, however, 

 considerable purulent infiltration of the cornea. This is fully as great 

 as in the case of exposures through a crown screen sufficient to injure 

 the corpuscles. 



Following an exposure of 20 minutes to the rays of the magnetite 

 arc passing through a water cell and concentrated by the quartz 

 double lens system, the following changes are seen: At the end of 10 

 hours the epithelium towards the periphery of the exposed area shows 

 changes similar to those seen after exposure through a crown screen. 

 As the central area is approached more marked changes occur; the 

 nuclei are seen to become extremely pycknotic and the cytoplasm 

 to stain intensely in eosin. Within the central area itself the super- 

 ficial layers have become desquamated, leaving usually only the basal 

 cells, which now consist of cylinders deeply stained in eosin from which 

 the nuclei have entirely disappeared. Within the most exposed area 

 at this stage the corneal corpuscles are still present in normal numbers. 

 Their nuclei show marked pycknosis, but the cytoplasm contains no 

 granules. Towards the periphery of the exposed area a few corpuscles 

 containing granules are seen. The corneal stroma is swollen to a 

 third more than its normal thickness, and stains less deeply in eosin. 

 Unless the sections are very thick the stroma is apt to fall out of 

 them. The individual lamellae are still recognizable but are greatly 

 distorted, due no doubt to not holding their positions in the cutting 

 of the sections. The endothelium is still adherent, but appears com- 

 pletely necrotic in the exposed area, the neuclei being pycknotic and 

 the cytoplasm staining deeply in eosin. 



After four days the epithelium is found to be reformed. Within 

 the most exposed region the corneal corpuscles are completely invis- 

 ible and the endothelium is absent. At the periphery of the exposed 



