[Postmortem behavior of the rheobase]

Own investigations on the postmortem rise of muscular threshold were conducted on 20 bodies with exactly known time of death. Muscular contraction was objectified using a sensitive force transducer. The muscle was excitated using rectangular impulses of 1 second duration of a current intensity which produces a force of muscular contraction of 2.5 mN. These excitations were continued over the postmortem interval until a current intensity of 80 mN doesn't cause a contraction of 2.5 mN any more. Investigations were mainly performed at the thenar muscles. There is a linear relationship between ln of muscular threshold (current intensity) and the time since death (r = 0.965). For any case the linear regression line between ln of muscular threshold and time since death was calculated. With mean values for slope and intercept the time of death was calculated for each measured threshold. Extrapolation of the time since death with mean values also for the slope reveals a much more precise estimation of the time since death than an extrapolation with an individual slope as proposed by Joachim and Feldmann (1980). The method was proved on a random sample of 8 practical cases. The real time since death was always within the 95%-limits of confidence of the extrapolated time since death.