The Masters were strictly bound by contract to the _laborerium_. In some cases they were paid by the day. We find, on May 29, 1355, that the salaries of Masters were lessened by two soldi a day, and workmen by one soldo. Sometimes the Commune found them wine and rations; at others they were paid by the piece, by contract. On June 7, 1456, the _Provveditore_ writes--"It is desired that on no account shall any Master go to work outside the Opera, without the deliberation and consent of all four Operai. If any absent himself without this permission, he shall be considered as discharged." The schools attached to the _laborerium_ must have been very complete. They trained pupils in the three sister arts--architecture, sculpture, and painting. One sees the remains of them in the Belle Arti at Florence, Siena, and other towns, and the Academy of St. Luke at Rome. Not all the _Magistri_ were teachers, but there were certain of them who held office as Professors. Niccolò di Pisa was certainly one of these, and so were Cimabue and _Magister_ Giotto. This full art-education accounts for the artist of the Renaissance being such an all-round man. One finds a painter like Giotto, or a sculptor like Niccolò Pisano, building grand architectural works. Sometimes they graduated in all three arts, as did Landi, Giotto, and Leon Battista Alberti. When they graduated in the schools, they became _Magistri_ of the guild, and could then undertake commissions. Besides the _Magistri fratelli_, there were the undergraduates as it were; in old Latin documents they are written as _fratres_; below these were the novices or pupils. The workmen employed by them were quite unconnected with the guild, and were paid daily wages as manual labourers.