A mathematical treatment of the process of synthesis of protein material in the pancreas, and its secretion in response to secretin administration, has been developed. It was based on assumptions inferred from experimental data and from analogy with a suggested mechanism for the submaxillary gland, published previously. It leads to expressions that quantitatively describe the protein output in samples of pancreatic juice obtained under widely varied experimental conditions. Inferences concerning the fundamental character of certain glandular mechanisms may be drawn from the treatment. In addition it permits provisional calculation of various factors not directly observable in critical experiments, and suggests further problems in connection with the secretory processes.