Preparation of a fluorescent substance from the eye of the dogfish, Squalus acanthias

attempt to isolate the antipernicious. anaemia factor the intensity of fluorescence in the 4650 and 5220 A. regions might be used to estimate the haemopoietic activity provided that the active molecule had not been broken up in the process of concentration. However, as the factor is heat stable this is very unlikely and no evidence for such a splitting has been found by the authors. The true values for the percentage of active material in any given prepara- tion cannot be estimated with certainty until the chemical nature of the active substance has been established, and until it has been shown exactly how the tntensity of fluorescence and the haemo- poietic response vary with the concentration of active material. SUMMARY 1. The fluorescence spectra of a number of pre- parations containing the antipernicious anaemia factor have been investigated.