Provides that where any condition of impairment of health caused by Parkinson's disease, resulting in total or partial disability or death to a volunteer firefighter, where such volunteer firefighter successfully passed a physical examination on entry into such service or subsequent thereto, which examination failed to reveal any evidence of such condition, shall be presumptive evidence that such disability or death was caused by the natural and proximate result of an accident, not caused by such firefighter's own negligence; and was incurred in the performance and discharge of duty, unless the contrary be proven by competent evidence.