The problem of the body's inner and external worlds, from natural history to the pathological reaches of physiology, is treated in this book, which establishes itself as a guide. Tobias Cheung focuses on the historical moment at which it is possible to obtain in the same breath both life and death in order to correlate and distinguish them from each other. He demarcates health and disease as normal and abnormal states, and explains changes in the history of the interactions between internal systems and their external worlds.