In studying the inner organism and structure of the edifice, one soon sees how recklessly the original fabric was constructed and in how many places it had to be rebuilt, strengthened and propped,--indeed, immediately after its completion. Here, as was the general custom in the greater early Gothic cathedrals, the building began with the choir and Capilla Mayor, to be followed by the transepts, the portions of the edifice essential to the service. The choir was probably temporarily roofed over and the nave and side aisles followed. The exterior façades, portals, and upper stories of the towers were carried out last of all by the aid of indulgences, contributions, alms and concessions. In old manuscripts and documents which record the very first work on the cathedrals we find the one in charge called "Maestro,"--or _magister operis_, _magister ecclesiae_, _magister fabricae_, but not till the sixteenth century does the appellation "arquitecto" appear. His pay seems to have varied, both in amount and in form of emolument,--sometimes it was good hard cash, often a very poor or dubious remuneration, handed out consequently with a more lavish hand; sometimes grants, and again royal favor. Generally the architect entered into a stipulated agreement with the Cathedral Chapter, both as to his time and services, before he began his work. We find Master Jusquin (1450-69) receiving from the Chapter of Leon not only a daily salary but also annual donations of bushels of wheat, pairs of gloves, lodgings, poultry, other supplies, and the use of certain workmen. Leon's unquestionable French parentage is, if possible, even more obvious in the interior than in the exterior. The piers between nave and side aisles are cylindrical in plan, having in their lowest section on their front surface three columns grouped together that continue straight up through triforium and clerestory and carry the transverse and diagonal ribs of the nave. They have further one column on each side of the axis east and west and, strange to say, only one toward the side aisles, which thus lack continuous supports for their diagonal ribs. The outer walls of the side aisles are formed by a blind arcade of five arches, surmounted by a projecting balcony or corridor and a clerestory subdivided by its tracery into four arches and three cusped circles. The nave triforium consists of a double arcade with a gallery running between (one of the very rare examples in Spain). Each bay has in the triforium four open and two closed arches, surmounted by two quatrefoils. The clerestory rises above, divided by marvelously slender shafts into six compartments and three cusped circles in the apex of the arch. Here shine, in dazzling raiment and with ecstatic expressions, the saints and martyrs ordered in the fifteenth century from Burgos for the sum of 20,000 maravedis.