Here is an example within the writer's immediate knowledge: At the age of seventeen a boy entered the service of one of the large railway systems as a clerk in the passenger department. Through eleven years of enthusiastic and concentrated endeavor to master the details of the service he rose to the head of the clerical force--that is, the reiterated impression upon his brain cells of the functions of the passenger service led to that co-ordination which resulted in efficient action. Then he became employed in the office of a large coal-mining company. For several days it was with the utmost difficulty that he could bring his attention to bear upon the new tasks. While seated at the desk in the coal office the old railway problems would chase through his mind; when he began to write the initials of the Pittsburg Consolidated Coal Company, he would find that he had written the initials of the Pittsburg, Cincinnati, Chicago and St. Louis Railway Company; instead of the initials of the Pittsburg, Fairport and Northwestern Dock Company, the initials of the Pittsburg, Fort Wayne and Chicago Railway Company. The latter initials in each case would appear upon the paper before he knew it, actually without his knowing that he had written them. The entirely unfamiliar routine entailed by the custody of bank accounts, coal leases, deeds and contracts, reports of coal shipments, and the handling of vouchers, became adjusted in his brain bit by bit through many weeks, and it was months before he could co-ordinate the new impressions into broad and well-defined reasoning. If he had been utterly hungry through all the period of the new service, it might have taken years.