This was the Guild of Saint John and Saint Luke; and every painter, miniaturist, illuminator, rubricator, copyist, maker of vellum, binder or seller of books who lived and worked in Bruges was obliged to belong to this Guild. This rule, which existed in Ghent, Antwerp and most artistic centres, had a double use; on the one hand it protected the individual illuminator from wrong and oppression of any kind; and, on the other hand, it tended to keep up a good standard of excellence in the work which was executed by the Guild-members. _Rules of the Guilds._ No miniaturist could be admitted till he had laid before the Dean of the Guild a sufficiently good sample of his skill, and all members were liable to be fined if they used inferior materials of any kind, such as impure gold, adulterated ultramarine or vermilion and the like. In this way the officers of the Guild acted as moderators between the artisan and his patrons, securing reasonable pay for the artist, and, in return for that, reasonably good workmanship for his employer or customer. The Guilds also prevented anything like commercial slave-driving by limiting very strictly the number of apprentices or workmen that each master might employ. _Decadence of MS. art._ Thus it happened that, though fine manuscripts were still written and illuminated in many of the principal monasteries of Europe, a large class of secular illuminators grew up, especially in Paris and the chief towns of Flanders and northern Germany. In this way the production of manuscripts, especially illuminated _Books of Hours_, became a regular commercial process, with the inevitable result that a great deal of work of a very inferior character was turned out to meet the rapidly growing demand for cheap and showy books. An immense number of these cheap manuscript _Horae_ were produced after a few fixed patterns, with some mechanical dulness of repetition in every border and miniature with which they were decorated. _Costly Horae._ At the same time manuscripts were still produced, mostly at the special order of some royal patron or wealthy merchant, which, in elaborate beauty and in unsparing labour of execution, are hardly surpassed by the work of the earlier monastic scribes[229]. Examples of this are mentioned above at pages 135 and 169. The Dukes of Burgundy and the Kings of France, towards the close of the fourteenth and the first half of the fifteenth century, numbered many illuminators among their regular paid adherents. In some cases the artist was permanently engaged, and passed his whole life in the service of one Prince; while in other cases famous illuminators were hired for a few months or years, when the patron wanted a specially magnificent manuscript either for his own use, or as a royal gift on the occasion of a marriage, a coronation or other great event. _Women artists._