PLATE 4. 



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Fig. 13. 



Fig. 12. 



Figure 11. Exp. 78. Magnetite arc. Double lens system, water cell, 

 flint glass screen (298 /u/x), exposure 1 liour. 



Showing retinal ganglion cells of rabbit unaffected 48 hours after exposure. 

 Thionin stain. Photo. X 706. 



Figure 12. Exp. .53. Magnetite arc. Single lens system, water cell, 

 crown glass screen (295 n^x), exposure 12 minutes. 



Heat effect on retina after 48 hours. In the affected area the rods and cones 

 are disintegrated and the nuclei of the nuclear layer are fragmented. The 

 inner layers of the retina are normal. Photo. X 42. 



Figure 13. Same experiment. Affected portion of retina under higher 

 magnification. Photo. X 190. 



Fig. 14. 



Figure 14. Exp. 98. Sunlight concentrated by large mirror. Water cell, 

 no screen. Exposure 14 seconds. 



Intense heat effect on retina after six days. On the left, the retina is normal. 

 On the right, the outer layers including the rods and cones are coagulated and 

 retain their forms, while the inner layers are disintegrated, the heat here having 

 been insufhcient to coagulate them. For the same reason the entire thickness 

 of the retina is disintegrated at the margin of the affected area. The choroid 

 shows a large hemorrhagic extravasation. Photo. X 28. 



814 



