For centuries, physicians observed that certain disorders were hereditary: they "ran in the family." Genetics and Medicine is the first comprehensive historical study to examine the close professional relationship between British scientists studying the nature of heredity and the practicing physicians of the day. In the 17th century, scientists and physician members of the Royal Society investigated the interaction of human heredity and disease. The biologists Charles Darwin and Francis Galton both had medical training and worked closely with physicians during the 19th century to define specific patterns of inheritance for a variety of inherited disorders. The application of Gregor Mendel's theory of heredity after 1900 by the geneticist William Bateson and the statistician Karl Pearson furthered the close collaboration between scientists and physicians during the decades before World War II that has defined the present-day understanding of the scope of modern "medical" genetics.