An apparatus for measuring biopermeability comprises a frame 4, a light source 1, a light detector 3, a pre-amplifier 5, an amplifier 7 and a DC meter 9. The light source 1 and the light detector 3 are secured to the frame 4 and face each other across a gap 6 into which an organism 31 e.g. a finger being measured can be received without applying any pressure. The gain of pre-amplifier 5 may be switched between unity and 100. The amplifier 7 is provided with zero and sensitivity adjustments and has a DC output terminal 8 from which DC output data representing biopermeability is provided. An AC amplifier circuit 13 may also be provided, as may a data processing unit 300 for automatic data processing of the DC and AC output data. <IMAGE>
APPARATUS FOR MEASURING OPTICAL TRANSMISSIVITY