The minute study of morbid organisation as a factor in the genesis of crime which has been extensively pursued in recent years has been for the most part concerned with conditions of arrested or distorted cerebral development, with the different forms and degrees of innate defect. Less attention has, on the whole, been given to the other large class of neuropathic criminals, those in whom the morbid aptitude for criminal acts is connected with deterioration of brain, where the mental defect is acquired.