(_a_) The problem of industrial hygiene and industrial disease. (_b_) The problems of school hygiene and school medicine, since school life is the industrial life of the child, who even receives wages for going to school in some communities. (_c_) The industrial and psychological problems of those who are maimed by accident, war, or disease. (_d_) The problem of industrial insurance and health insurance. All of these questions involve matters of State action, legislative control, and economic reform with which I do not wish to deal. But I wish to make it clear, in closing this chapter, that the social worker as a citizen is as much interested in these hopes for radical economic reforms as any one else can be, though she does not regard them as her special business. Preventive medicine and the daily fight against individual cases of disease which we hope some day to prevent--these two activities go on side by side, each helping the other. The social worker corresponds to the private practitioner of medicine; the economic reformer and discoverer corresponds to the laboratory student of preventive medicine or to the public health official. In social work as in medicine the case worker should bring to the inventor and reformer new facts and illustrations suggestive of the evils to be reformed or possibly of the ways of combating them. And in the difficult, often disappointing, task of trying to help individuals, the case worker will also take part of his inspiration from the hopes and ideals of a better economic order sketched for him by the legislative reformer. The method and technique of economic investigation is complex and difficult. For a masterly treatment of this and all other aspects of social diagnosis Miss Mary E. Richmond's epoch-making book on "Social Diagnosis" should be consulted. (Published by the Survey Associates in New York City.) CHAPTER IV MENTAL INVESTIGATION BY THE SOCIAL ASSISTANT Ever since the days of Charcot, France has been the land of medical psychology. France has never failed, as other countries have failed, to take full account of the mental factors, the mental causes and results in disease.