Motility is a fundamental property of living systems, from the cytoplasmic streaming of unicellular organisms to the most highly differentiated and de veloped contractile system of higher organisms, striated muscle. Although of motility have a long and in scientific investigations into the mechanisms teresting history, the knowledge of molecular processes, especially in the area of regulation of control of motility, has been developing at an ever more rapid pace with the utilization of multidisciplinary approaches from physiology, cell biology, genetics, biochemistry, pharmacology, and biophysics. In Volume 3, Cell and Muscle Motility continues the same philosophy as that of the preceding volumes. The essays are meant to focus on topics of current interest, to be critical rather than exhaustive, and to indicate the current trends of research efforts. The series is intended to foster an in terchange of concepts among various workers in a variety of disciplines and to serve as a reference for students and workers who wish to familiarize them selves with the most current progress in motility. Robert M. Dowben Jerry W. Shay Dallas vii Contents Chapter 1 Intermediate Filaments in Striated Muscle: A Review of Structural Studies in Embryonic and Adult Skelttal and Cardiac Muscle Maureen C. Price and Joseph W. Sanger 1. Introduction ................................................ .