1. A method is described whereby the major components of liver suspensions are segregated according to size into three main fractions: (a) a large granule fraction composed of elements approximately 0.5 to 2 µ in diameter; (b) a microsome fraction composed of submicroscopic elements approximately 80 to 150 mµ in diameter; and, (c) a supernate fraction containing the soluble components of the extract.