Clumsy as it was, however, the Aztec picture-writing seems to have been adequate to the demands of the nation, in their imperfect state of civilization. By means of it were recorded all their laws, and even their regulations for domestic economy; their tribute-rolls, specifying the imposts of the various towns; their mythology, calendars, and rituals; their political annals, carried back to a period long before the foundation of the city. They digested a complete system of chronology, and could specify with accuracy the dates of the most important events in their history; the year being inscribed on the margin, against the particular circumstance recorded. It is true, history, thus executed, must necessarily be vague and fragmentary. Only a few leading incidents could be presented. But in this it did not differ much from the monkish chronicles of the dark ages, which often dispose of years in a few brief sentences,--quite long enough for the annals of barbarians.[152] In order to estimate aright the picture-writing of the Aztecs, one must regard it in connection with oral tradition, to which it was auxiliary. In the colleges of the priests the youth were instructed in astronomy, history, mythology, etc.; and those who were to follow the profession of hieroglyphical painting were taught the application of the characters appropriated to each of these branches. In an historical work, one had charge of the chronology, another of the events. Every part of the labor was thus mechanically distributed.[153] The pupils, instructed in all that was before known in their several departments, were prepared to extend still further the boundaries of their imperfect science. The hieroglyphics served as a sort of stenography, a collection of notes, suggesting to the initiated much more than could be conveyed by a literal interpretation. This combination of the written and the oral comprehended what may be called the literature of the Aztecs.[154]