An attempt was made to analyze differences in the results obtained by various kinds of finger plethysmography, such as penetration photo-electric plethysmograph (penet.-PTG), reflexion photo-electric PTG (refl.-PTG), mechanoelectric PTG (pneumo-PTG and hydro-PTG) and impedance PTG, by taking simultaneous recordings principally from the same finger tip. Comparisons of the time course (onset time...