Many investigations have been made as to the destruction of red blood corpuscles in the spleen, and there can be little doubt that this occurs. If the hæmoglobin set free is also destroyed in the spleen, iron in some form will be liberated. The presence of iron in the spleen has already been shown by various observers, but the exact nature of the substances with which it is combined is still a matter of doubt.The object of this investigation was, if possible, to trace the stages in the decomposition of hæmoglobin as shown by the existence of intermediate compounds, and to ascertain the chemical nature of such compounds.