Estimation of the average swimming speeds of microorganisms by using a simple technique

A method for estimating average speeds of swimming cells has been described. The statistical counting technique based on treating the swimming cells as a dilute gas, and its accuracy has been confirmed by direct measurements. In principle this technique can be applied to any suspension of cells satisfying certain statistical criteria [theory] enough to exert no force on each other except contact forces at the instant of collision. The mean free path is inversely proportional to the concentration of the cells in culture. This definition is readily seen to satisfy the statistical assumptions