Based on forty years of clinical practice, Julian Barker formulates a number of interlocking ideas that integrate circadian physiology with the transformations that constitute human life. Taking knowledge, information, and data from various disciplines, he presents an integrative model of health, linking circadian biology with the psychosocial human being. He develops a theory that attempts to explain how medicinal plants modify human physiology and how they contribute to health. Aimed at the student acquiring knowledge and developing the skills to practise medicine as well as the qualified herbal practitioner, this thought-provoking work breaks new ground in health theory.