This second edition has been updated, reflecting new knowledge in the field and including several new topics: a discussion of endorphins and neuroregulators, a section on oncogenes and another on toxic-shock syndrome, and a discussion of AIDS. As with the first edition, a conceptual adaptation approach is used throughout, and the emphasis is on mechanisms by which pathogenic agents disrupt homeostasis and mechanisms by which the body maintains or restores homeostasis. Sufficient facts and details are provided to enable students to understand the mechanisms and principles involved, rather than merely providing a list of signs and symptoms. Also new to this edition are 'behavioral objectives' at the start of each chapter and review questions at the end of each unit that integrate information from several chapters. In addition, this edition contains many more illustrations.