Darwin broke with previous traditions in physiognomy. His notebooks and correspondence contain references to earlier works in the field, such as the Fragments of Physiognomy of Johann Caspar Lavater. Darwin owned the ten-volume French edition, with its twenty-four images illustrating a frog metamorphosing into Apollo.  Another significant work was the Anatomy and Philosophy of Expression as Connected with the Fine Arts, by the Scottish physician Sir Charles Bell. Bell’s work aroused Darwin’s interest in the subject and Darwin referred frequently to the third edition in Expression. Darwin’s research however pointed to shared evolution with animals, in contrast to Bell who proposed that humans had unique, divinely created muscles in order to express uniquely human emotions.