the able help of my colleague Stanley Paulson. I dedicate this book to the memory of my late brother, Dr. chern. Erwin Spiegelberg, at the time of his death assistant professor at the University of Rio de Janeiro, who preceded me by two years in emigrating from Nazi Germany. When in 1938 he put an end to his life in an apparent depression, he also did so in order not to become a burden to his brothers, who were on the point of following him. Whatever I, more privileged in health and in opportunities in the country of my adoption, have been able to do and achieve since then has been done with a sense of a debt to him and of trying to live and work for him too.