A non-graduate student in arts was, before admission, expected to know Latin, and, on admission, apprenticed to a master or doctor who acted as a tutor in scholastic matters: in 1276 this system of apprenticeship was made compulsory. The full medieval course lasted several years. Students who entered as boys stayed, if they took the full course, till they were grown men, gradually taking up teaching as part of their course of study. The bachelors may have assisted in the education of the younger arts students and of the glomerels who are mentioned below, but normally instruction in the arts course was given by masters, and in the higher faculties by doctors. The degree of master was a license to teach, and newly created masters were required to teach and to reside for two years (or later at least one year) for that purpose. This pre-reformation scheme is in marked contrast to the modern plan where the students enter as young men, all of about the same age, with a normal course lasting three years or so, and with their studies sharply differentiated from those of a limited number of post-graduate and research students and of a separate body of teachers. Mullinger estimated that during the medieval period the number of resident regents varied from one hundred to two hundred, and the number of students (apparently exclusive of monastic students) never exceeded two thousand of whom the great majority were of humble birth; no doubt there were wide variations in the numbers at different times. The history of Guilds in the University cannot be given with any certainty. It may be that in the early years of the University most secular students and teachers from any particular locality were associated together as a guild, and perhaps every student on arrival was expected to join his local guild, and through it become a member of the University. The guilds imposed on their members definite rules for their conduct in relation to one another, and enforced such regulations by means of money fines, refusal of assistance, and in extreme cases expulsion. The relations between the members of different guilds were, however, often unfriendly or worse; in particular there was constant friction between the guilds connected with localities north and south of the Trent. It has been suggested that at one time one of the proctors represented the cis-trentine guilds and the other the trans-trentine guilds: this seems to have been the case at Oxford, but there is no evidence of such a custom at Cambridge where, according to Peacock, these trentine disputes were less violent than at the sister University.