CYTOCHROMES and other catalysts capable of yielding haematin are widely distributed in living tissues. It is, therefore, possible a priori that many tissues will give a positive reaction in the luminescence test with o-amino phthalic acid cyclic hydrazide ('luminol') when treated in some way which will lead to the formation of haematin. However, in the forensic application of the test it has generally been found that vegetable matter, either fresh or rotting, gives a negative reaction1.