The author has carried on extensive research on the role of hereditary factors in the development of laboratory rodents, especially the mouse. He previously published a book entitled " The Genetics of the Mouse." He has, in addition, a long list of papers to his credit which deal primarily with new mutation or inherited variations in the laboratory mouse. He may therefore be considered well grounded in the subject which he develops. The last short paragraph of the book reads as follows: " The study of inherited diseases in animals is a new branch of medical science. If this book will convince a few people of the value of this new tool for aetiological studies it will have fulfilled its purpose. " This paragraph states in essence the content and purpose of the book.
After three introductory chapters on general principles, the author devotes six