1. Light stimuli affect the alpha rhythm according to the "all or none" law.2. Light stimuli have a delayed reaction time in short petit-mal attacks.3. Light stimuli are not perceived in long petit-mal attacks.4. Both light and sound stimuli tend to terminate moderately severe petit-mal seizures-the sound being much more effective.5. When both fail to provoke a response, unconsciousness may be presumed.6. This method of determining the impairment of consciousness may be useful in:(a) Estimating the severity of petit-mal seizures.(b) The effectiveness of anticonvulsant therapy on the spells.