The author is convinced from perusal of current medical writings in this country that there is need among American physicians for a work presenting the subjects of Digestion and Metabolism in a popular manner, without technical details, and from the standpoint of dynamics rather than from that of analytical statics usually occupied by text books of physiological chemistry. He has rewritten in the form of a concise and systematic treatise the substance of his lectures in this field. No effort has been made to prepare an encyclopedic survey or a methodic synopsis of the very extensive literature of these subjects, but rather to offer a practical interpretation of them in their present state of development. The aim of the book is to describe the chemical changes in normal and abnormal digestion, and explain the known metabolic modifications that food materials undergo within the body. This understanding makes for comprehension of the pathology of diseases that may be termed metabolic — such as gout, diabetes, nephritis, autointoxication and the results of indigestion. In a word, the aim is to give the student and practitioner a working knowledge of just what is known to occur in the chemistry of the normal body and also of the changes concerned in many widespread and important diseases. Variations and findings in morbid states have been everywhere considered. The student and practitioner of the art and science of medicine will gain the most definite idea of physiological processes and chemical functions if they View them as a moving picture; in other words, if they will consider them dynamically rather than statically. The experimental method alone has enabled us to acquire the larger portion of our present knowledge of digestion and metabolism. Ability to think in the terms of the experimental method is essential to an under standing of these subjects. The student and physician need more than facility in method, invaluable as this is. They need the dynamic concept of function on which to found a dynamic conception of disease. The definition of experiment is fundamental to the concept of function.