This book comes from the reflections and experience of more than forty years spent in court. Aside from the practice of my profession, the topics I have treated are such as have always held my interest and inspired a taste for books that discuss the human machine with its manifestations and the causes of its varied activity. I have endeavored to present the latest scientific thought and investigation bearing upon the question of human conduct. I do not pretend to be an original investigator, nor an authority on biology, psychology or philosophy. I have simply been a student giving the subject such attention as I could during a fairly busy life. No doubt some of the scientific conclusions stated are still debatable and may finally be rejected. The scientific mind holds opinions tentatively and is always ready to reexamine, modify or discard as new evidence comes to light.