700 VERHOEFF AND BELL. 



tion. Enucleation at end of 6 days. Fundus shows burned area just 

 beneath optic (Hsc. Lens epitheHum normal. 



Experiment 99. Blue uviol screen. Water cell. x\lbino. Ex- 

 posed 1| minutes. No inflammatory reaction. Enucleation at end 

 of 12 days. Fundus shows burned area undergoing repair. Cornea, 

 lens epithelium, and iris normal. 



Experiment 100. Blue uviol screen. Water cell. Albino. Total 

 exposure, 10 minutes, one second on, one second off. No inflamma- 

 tory reaction. Enucleation at end of 7 days. Retina shows no 

 burned areas. Cornea, lens epithelium, and iris, normal. 



Experiment 101. Blue uviol screen. No water cell. Pigmented 

 eye. 220 exposures, I second each, with intervals of 1 to 3 seconds. 

 No inflammatory reaction. Fundus normal. 



Character of the Thermic Effects Produced in the Retina. 



In the experiments in which the pigment epithelium alone was 

 affected no changes were noted macroscopically. In most of the other 

 experiments the lesions could be seen with the ophthalmoscope or 

 better still on opening the eye after enucleation. They appeared as 

 sharply defined reddened spots. Some of those obtained after ex- 

 posure to sunlight showed blood extending from them into the vitreous 

 humor. Some of the spots were observed only after the eye was 

 placed in Zenker's fluid. In Experiment 96 in which a burned area 

 involved the optic disc, there was intense hemorrhagic retinitis ap- 

 parently due to thrombosis of the central vein. The spots produced 

 by sunlight measured about 2.5 mm. in diameter. Those produced 

 by the magnetite arc and single lens system were about 3 mm. in 

 diameter as measured under the microscope with reference to the 

 effects on the pigment epithelium, but only about 1 mm. in diameter 

 as measured with reference to the effects on the retina proper when 

 this was involved. This concentration of the effects in the center of 

 the area was no doubt due to two facts, one being that the light was 

 actually more intense here, and the other that towards the periphery 

 of the area the heat generated in the pigment epithelium became 

 rapidly dissipated. 



Microscopical: The most striking feature of all the burned areas 

 whether due to long or short exposures was their sharp demarcation, 

 illustrating again here as in ^e case of the cornea how sharply critical 



