Humanist grammar [secondary] schools were established in London by merchants and guilds. Classical Latin and Greek were taught and the literature of the best classical authors was read. Education was opened up to women. Secondary education teachers were expected to know Latin and Greek and have studied the ancient philosophers, history, and geography. The method of teaching was for the teacher to read text-books to the class from a prepared curriculum. The students learned how to read and to write, to develop and amplify a theme by logical analysis, and to essay on the same subject in the narrative, persuasive, argumentative, commending, consoling, and inciting styles. They had horn-books with the alphabet and perhaps a Biblical verse on them. This was a piece of wood with a paper on it held down by a sheet of transparent horn. Disobedience incurred flogging by teacher as well as by parents. Spare the rod and spoil the child was the philosophy. There were two week vacations at Christmas and at Easter. Oxford University was granted a charter which put the greater part of the town under control of the Chancellor and scholars. The mayor of Oxford was required to take an oath at his election to maintain the privileges and customs of the university. Roman law Regius professorships were founded by the King at Oxford and Cambridge. The physicians of London were incorporated to oversee and govern the practice of medicine. A faculty of physicians was established at Oxford and Cambridge. Only graduates of the new College of Physicians or of Oxford or Cambridge may practice medicine or surgery. Food that was digested was thought to turn into a vapor which passed along the veins and was concreted as blood, flesh, and fat. Geoffrey Chaucer's "Canterbury Tales" was a popular book. Through Chaucer, London English became a national standard and the notion of "correct pronunciation" came into being. The discoveries and adventures of Amerigo Vespucci, a Portuguese explorer, were widely read. The North and South American continents were named for him.