The first paper deals with the causes of crime, the anatomical abnormalities found in criminals, and the method of treatment best calculated to enable him to adjust himself normally to the outside world on his discharge. A criminal act is defined as an act which does not conform to the standard of conduct accepted by the age in which the criminal is living. The author divides criminals into the following classes: (1) The political criminal; (2) the criminal by passion whose crime may be the only one in his life; (3) the insane criminal, many of whom have been punished for their madness by being sent to prison; (4) the instinctive or born criminal; (5) the professional criminal who deliberately chooses his mode of life; (6) the occasional criminal.