Ultrasonically-Induced Movements in Cells and Cell Models

Normal- and high-speed cinemicrographs of events resulting from highly localized 25-kc vibration of small regions of an individual cell wall in Elodea leaf cells and in plastic cell models are discussed. In plant cells, complex patterns of ordered agitation are set up, similar to parts of the patterns observed in model cells. In models containing Newtonian fluids, steady circulation results with streamline positions and directions being functions of viscosity and the vibration pattern of the wall, the general features being accounted for by the theory of acoustic streaming. In models containing weak agar gels, a combination of plastic and fluid behavior is observed as setting ensues; immediately after vibration begins, suspended particles ``flow´´ for a short distance following the streamlines of a viscous fluid, with displacement vectors distributed like the velocity vectors in acoustic streaming, but, as the sound ceases, return slowly almost to their original positions.