Some Properties of the Fluorescence of Fish Muscle

White muscle of a fish in prerigor condition fluoresces when irradiated with ultraviolet light of 366 mμ. Investigations carried out with the white sucker (Catostomus commersoni) indicate that the fluorescence is destroyed by treating the muscle with dilute acids. Emission spectra of fluorescence show a peak at about 460 mμ. Prerigor muscle also reduces a tetrazolium salt (Nitro BT) to its colored formazan. From these observations it is suggested that reduced pyridine nucleotides are at least partly responsible for the fluorescence of prerigor muscle.