644 VERHOEFF AND BELL. 



for a liminal reaction. It was found also that if an exposure sufficient 

 to produce a slight reaction, was followed within 24 hours by a sub- 

 liminal exposure, the total effect was considerably greater than that 

 produced in the control eye by a continuous exposure of the same 

 total length. 



Experiments. 



effect of previous reactions upon sensitiveness of eye to 

 subsequent exposures. quartz mercury vapor lamp. 



Experiment 32. Distance .5 meter. Albino rabbit. Right eye 

 exposed 4 minutes. After 24 hours, slight reaction (animal unusually 

 sensitive). Right eye exposed 2 minutes. Left eye exposed 6 min- 

 utes. Results: Right eye, increased reaction with loss of corneal 

 epithelium. Left eye, moderate reaction without loss of corneal 

 epithelium. 



Experiment 33. Distance .5 meter. Right eye exposed 5 minutes. 

 Result: Very slight reaction. One month later. Right eye exposed 

 3| minutes. Result: Moderate conjunctivitis, marked stippling of 

 cornea. 



Experiment 34. Right eye exposed 5 minutes at .5 meter. Left 

 eye exposed 7| minutes at .5 meter. Results: No reaction in either 

 eye. 14 days later. Right eye exposed forty minutes at 35 cm. 

 through crown screen. Left eye exposed 4 minutes at 35 cm. with- 

 out screen. Results: Slight reactions, more marked in left eye. 8 

 days later. Right eye exposed 3 minutes at .5 meter. Left eye 

 exposed 4 minutes at .5 meter. Results: Slight reaction in each eye. 

 More marked in right. 



Experiment 35. Distance .5 meter. Left eye exposed 7| minutes. 

 Result: Reaction. 26 days later. Left eye exposed 4 minutes. 

 Result: Slight reaction. 



Experiment 36. Right eye exposed 1| hours at 20 cm. through 

 crown screen. Result: Marked reaction with keratitis, lasting over 

 2 weeks. 5 weeks later. Left eye exposed 2 minutes at .5 meter. 

 Result: No reaction. 



