This is the fully revised and updated fourth edition of the acclaimed Animal Physiology, a survey emphasizing fundamental principles. The text is written for those who want to know how things work, what animals do, and how they do it. The book deals with such traditional physiological subjects as respiration, circulation and digestion, arranged according to major environmental features: oxygen, food and energy, temperature, and water. This fourth edition has been updated in all chapters where there is essential new information, yet the general outline of the book remains the same. As a new feature, each chapter now begins with a brief synopsis, outlining its essential features and the fundamental principles to be discussed. There are nearly two hundred new references, chosen with an emphasis on recent developments. It incorporates discussions of recent research including deep sea rift animals, hearing in fish, and gas exchange in eggs. The book is aimed at upper level college students and graduate students of comparative physiology.