... how great the stammerer's knowledge may be, he often appears to be illiterate simply because he is unable to express himself in words. His knowledge is locked up by his infirmity, the same as though he had a steel band drawn over his mouth and fastened with a padlock which he is unable to unlock for want of a proper key. The man with the locked-up knowledge is under as great a handicap ... — Stammering, Its Cause and Cure • Benjamin Nathaniel Bogue