A seminal work aiming to codify the physiology of digestion before the discipline formally existed. Synthesising observation, proto-chemical theory, and mechanical models of the body, Arbuthnot traces alimentary processing from mastication through gastric liquefaction, bile action, pancreatic and intestinal secretions, peristalsis, lacteal absorption, and mesenteric filtration. He advances the then-novel view that digestion is an active chemical–mechanical system rather than passive putrefaction, anticipating later metabolic and biochemical theory by over a century. With its analysis of saliva as a reactive agent, the stomach as an emulsifying chamber, bile as the primary digestive catalyst, and the intestines as dynamic absorptive machinery, the treatise constitutes one of the earliest unified models of internal bodily economy. Inscription on ffep; small stain to title page; pages clean throughout; cover slightly crooked. A foundational, forward-looking work in the proto-history of nutritional and physiological science.