The main support for the theory of mental illness as regression which dominated psychiatric practice for several decades. Morel described and illustrated the nature, causes, and signs of human degeneration. He focused on physical signs but also included various intellectual and moral deviations. This led to the classification of criminals and geniuses as types of degenerates or deviates along with the insane and neurotic. Morel emphasized the hereditary factor and his work helped bring about a deemphasis on therapeutic work in the psychiatry of his time. The atlas reproduces by lithography some of the earliest photographs of the insane.