VII. On the relations of turacin and turacoporphyrin to the colouring matter of the blood

In a recent paper read before the Royal Society, I have shown that the intense absorption band in the extreme violet, which is observed, by means of photography, in the spectrum of highly diluted solutions of hemoglobin and its compounds, is (with slight changes in its position) exhibited by certain of the derivatives of the blood colouring matter,e. g ., by hemochromogen and the compounds of hematin, and by that remarkably interesting coloured but iron-free derivative of the latter body, hematoporphyrin.