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ACTIVE salt absorption is a fundamental characteristic of the living cell. In tissues and whole organisms the active transport of salts from specialized absorption organs to other parts of the body is clearly a matter of fundamental importance. The cellular mechanism of active transport of water and salts is probably similar in plants and animals ; but plants are in several respects more convenient objects for experimental investigation.

The properties of the cytochromes a and a3 were studied in suspensions of baker's yeast and compared with spectrograms of a heart-muscle preparation. The results corroborate the original findings of Keilin and Hartree on the coexistence of two enzymes and show the identity of cytochrome a3 with cytochrome c oxidase. The individual spectra of the two enzymes were calculated according to the method of optical subtraction, applied to spectrograms from yeast treated with O2, N2, CO, HCN and various mixtures of these gases. Observations of the kinetics of cytochromes a and a3 were made with the aid of alternating reduction and reoxidation, with continuous recording of the band heights. Complete spectrograms were recorded in the automatic spectrophotometer. The role of cytochrome a3 in the aerobic respiration was studied by parallel observations of the oxidation-reduction state and the intensity of oxygen consumption.

WITH a recording microspectrophotometer of special construction, the absorption spectrum of a bundle of twenty to forty roots of wheat shows distinct bands of cytochrome c (Fig. 1). The bands of the cytochromes b and a + a3 are also recognized as elevations of the curve. The spectrum is calculated as the relation between the transparency of the roots in distilled water and the transparency after shifting over the medium to 0.001 M hydrogen cyanide, the cytochromes being partly in the oxidized state in the untreated roots. The reduction in hydrogen cyanide is due to the blocking of the cytochrome oxidase at still operating dehydro-genases. With carbon monoxide a broadening of the γ-band of cytochrome b is observed. Calculated from the absorption at λ 550 mµ the roots contain approximately 4 mgm. cytochrome c per kgm. fresh weight. The cytochrome system is present at all lengths of the roots of two–three weeks old seedlings. Also single roots of maize show similar spectra.