A method for accelerating marrow cell proliferation as set forth in claim 2, wherein the ??-galactosylceramide is represented by the following formula (II): ##STR34## wherein R1 is one of the substituents defined by the following (a) to (d), and R2 represents H or OH (X is defined in the following (a) to (d)): --CH2 (CH2)Y CH3 (a) when R2 is H, X is an integer of 0 to 24 and