Practically no historical accounts of the evolution of peer review exist. Biomedical journals appeared in the 19th century as personal organs, following the model of more general journalism. Journal editors viewed themselves primarily as educators. The practice of editorial peer reviewing did not become general until sometime after World War II. Contrary to common assumption, editorial peer review did not grow out of or interact with grant peer review. Editorial peer review procedures did not spread in an orderly way; they were not developed from editorial boards and passed on from journal to journal. Instead, casual referring out of articles on an individual basis may have occurred at any time, beginning in the early to mid-19th century. Institutionalization of the process, however, took place mostly in the 20th century, either to handle new problems in the numbers of articles submitted or to meet the demands for expert authority and objectivity in an increasingly specialized world.