Some Properties of the Pigment of Blepharisma

In connection with measurements of the metabolism of Blepharisma described in the preceding paper, the writer made certain observations on the red pigment of this organism. The pigment of the intact organism defies extraction with any of the common organic solvents, but it may easily be obtained in solution by macerating fresh cells in clean quartz sand and extracting with 90 per cent ethyl alcohol. The alcoholic extract behaves like an indicator. When neutral or acid, it is bright red, the color disappearing in alkali. The turning point is quite near neutrality, and only a slight degree of alkalinity is necessary to make the color-change complete. This may be brought about by adding a drop of M/10 sodium bicarbonate solution to 10 cc. of pigment solution. Perceptible changes in depth of color may be caused by merely varying CO, tension. Fig. 1 shows the absorption curve of the extract of 108 ram. 8 of cells made up to 10 cc. in ethyl alcohol. The curve was determined on a K6nig-Martens spectrophotometer. E, the extinction coefficient, is plotted against X, the wave-length in ~ . The spectrophotometer readings ~1 and ~2 are shown with their accompanying values of X and ~ in Table I. The curve might be compared with the figure published by E. Ray Lankester in 1873 for the absorption spectrum of the unextracted pigment of Stentor caeruleus. Since stentorin is blue and the pigment of Blepharisma red, their absorption spectra would not be expected to coincide. But the three maxima shown by the Blepharisma pigment in the short-wave-length end of the spectrum might be said to correspond to the three absorption bands of stentorin in the long-wave-length end of the spectrum.