Traditional methods of cultivation of micro-organisms provide little control over the ever-changing physical and chemical environments to which growing populations are exposed. The need for a variety of highly standardized conditions of growth and the selection of several new parameters to measure growth or cultural progress has been recognized. This volume describes the measurement and control of the physical and chemical factors that affect or indicate microbial activities, usually in homogeneous liquid culture. An introduction to the general principles of chemical and physical measurements and to the automatic recording and control of them is presented. Some chapters focus on the theoretical and practical aspects of techniques of continuous cultivation in the laboratory with indications of its application to research problems.