French chemist who worked with Antoine Laurent Lavoisier (1743-1794) in pioneering studies on metabolism. Séguin and Lavoisier described experiments on human metabolism in their "Memoir on Animal Respiration," which was published in 1789. During these metabolic experiments, Séguin served as the experimental subject. They measured oxygen absorption when Séguin was fasting, eating, resting, or exercising. During the course of these experiments, Séguin and Lavoisier made several fundamental observations. They realized that oxidation in human beings is dependent on food, environmental temperature, and mechanical work. These experiments established the basic facts of the theory of energy transformation.