I have prepared the following pages in response to the request of a number of physicians to give in a series of lectures a resume of those subjects in physical or general chemistry which are of importance in medicine.The fact that a large number of observations are described in modern medical literature that are based upon our newer conceptions of physical chemistry renders it imperative that the physician become acquainted with these theories and methods if he does not wish to have such observations and their practical applications remain a scaled book to him.These lectures are in no way a text-book of physical chemistry. I have merely endeavoured to show in them the close relation that exists between this new branch of chemistry and the biological sciences, and also, in response to the wishes of my hearers, to describe in some detail the more important methods of physical chemistry.The book may perhaps serve as an introduction to the study of the excellent text-books now available devoted to physical chemistry.Should the lectures contained in the following pages incite any one to a study of this subject and to its application to the medical sciences, the purpose of this volume will have been accomplished.