Mead, Smith & Williams (1955) introduced a method for the fluorimetric assay of ,B-glucuronidase activity; the method consisted of the enzymic hydrolysis of methylumbelliferyl (3glucuronide, followed by fluorimetric estimation of the liberated methylumbelliferone. Robinson (1956) synthesized methylumbelliferyl (3-glucoside and used it in the study of ,B-glucosidases from a variety of sources; like Mead et al. (1955), Robinson found the fluorogenic method convenient and extremely sensitive. Levvy, Hay & Marsh (1957) attempted to use methylumbelliferyl ,B-glucuronide in the study of limpet fl-glucuronidase; they found methylumbelliferone to be unstable, and so considered the method to be too exacting for general use.

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the oxygen uptake and acetoacetate oxidation when added alone or with fumarate, but not in the presence of a-oxoglutarate. The reasons for these differences are discussed. Anaerobically, relatively slight inhibitions of the reduction of acetoacetate were observed. 6. The oxidation of L(+)-p-hydroxybutyrate is inhibited by dinitrophenol, whereas that of the D(-)-form is not. This is related to the fact that only the L(+)-form requires conversion into the coenzyme A derivative. The differences in the behaviour of the Land D-forms towards dinitrophenol were used to examine the configuration of the P-hydroxybutyrate formed in sheep-heart muscle aerobically and anaerobically. In both cases the D-form only was found.

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