On Cytochrome, a Respiratory Pigment, Common to Animals, Yeast, and Higher Plants

Under the names myohaematin and histohaematin MacMunn (1884-1886) described a respiratory pigment, which he found in muscles and other tissues of representatives of almost all the orders of the animal kingdom. He found that this pigment, in the reduced state, gives a characteristic spectrum, with four absorption bands occupying the following positions: 615—593/567·5—561/554·5—546/532—511/. When oxidized, the pigment does not show absorption bands. In 1887 MacMunn described a method by which it can be extracted in a “modified form” from the muscles of birds and mammals. He found the pectoral muscle of a pigeon to be the most suitable material for the extraction of “myohaematin,” in the belief that it was the sole colouring matter of the muscles in a pigeon bled to death. From this “modified myohaematin” he also obtained other derivatives, such as acid haematin and haematoporphyrin, and he finally arrived at the conclusion that myo- and histohaematin are respiratory pigments different and independent from haemoglobin and its derivatives. In 1889 Levy carefully repeated MacMunn’s experiments in extracting myohaematin from muscles of birds and mammals and obtained the substance described by MacMunn as “modified myohaematin." But he regarded this substance as an ordinary haemochromogen, derived from haemoglobin.