642 VERHOEFF AND BELL. 



Experiments. 



effect of repeated exposures. quartz mercury vapor lamp 

 distance .5 meter. 



Siibliminal Exposures Repeated within 2.'+ Hours. 



Experiment 23. Right eye. Exposure 3f minutes. Interval 

 10 minutes. Exposure 3f minutes. Left eye. Exposed 7| min- 

 utes continuously. Result: Reaction in both eyes, more marked 

 in right. 



Experiment 24. Right eye. Exposed fi\'e minutes with four 

 intervals of one minute each. Left eye. Exposed 5 minutes continu- 

 ously. Result: Very slight reaction in each eye. 



Experiment 25. Right eye. Exposed 3 minutes. One hour inter- 

 val. Exposed 3 minutes. Result: Marked reaction. 



Experiment 26. Right eye exposed 3 minutes. Four hours inter- 

 val. Exposed 3 minutes. Result: Marked reaction. 



The next phase of the investigation dealt with subliminal exposures 

 at intervals of one or more days, such as might occur in actual use of 

 sources rich in abiotic radiation. The results show that an exposure 

 of one-sixth the liminal repeated every 24 hours for 52 days has no 

 visible effect on the cornea or conjuncti\'a. An exposure of one-third 

 the liminal repeated every 48 hours has a slight eifect on the cornea 

 after seven to nine exposures, which however gradually disappears 

 in spite of the exposures being continued. A daily exposure of one- 

 third the liminal begins to produce a reaction after six exposures. 

 The conjunctivitis disappears, but the corneal eflFect gradually in- 

 creases until after thirty-four exposures there is a marked central haze. 

 This leaves a slight corneal scar which is barely visible forty days after 

 the last exposure. An exposure one-half the liminal repeated at the 

 end of 24 hours produces the effect of a single liminal exposure. A 

 single exposui'e just subliminal, increases the sensitiveness of the eye 

 to abiotic radiation for over two weeks. On the other hand an 

 exposure one-sixth the liminal every 24 hours, or one-third the liminal 

 every 48 hours repeated for a long period of time, has the effect of 

 rendering the eye somewhat less sensitive to abiotic action. 



