The truth is that an army regularly officiating as a political body would require for its explanation two revolutions—one to bring it into existence and another to abolish it; but of both cataclysms history is silent. The growth of the political from the military organization was somewhat as follows. After the Romans had determined to use the centuries regularly as voting units for the decision of questions not purely military, they proceeded forthwith to extend the organization so as to include all the citizens. For this purpose the men of military age who were free from duty for the time being, or who had served the required number of campaigns—sixteen in the infantry or ten in the cavalry[1214]—or who were exempt on account of bodily infirmity or for any other reason, had to be admitted to the junior centuries, thus materially increasing their number and making them unequal with one another. In a state, too, in which great reverence was paid to age the seniors could not be ignored. They were accordingly organized in a number of centuries (84) equal to that of the juniors—an arrangement which made one senior count as much as three juniors.[1215] The mechanics who were liable to skilled service in the army[1216] were then grouped for voting purposes in two centuries, that of the smiths and that of the carpenters,[1217] based on the two guilds in which these artisans were already organized.[1218] Authorities differ as to the classes with which they were associated. Livy[1219] adds them to the first class. Cicero,[1220] too, places a century of carpenters with that group, making no mention of the smiths, whereas Dionysius[1221] assigns both centuries of mechanics to the second class. The explanation of the difference of opinion seems to be that information as to this point was not contained in the censorial document from which the annalist (Fabius Pictor) drew his knowledge of the earlier comitia centuriata; the Romans knew only by tradition that the industrial centuries were associated in the assembly with one of the higher classes. The weight of authority inclines in favor of the first class, and the reason for the respectable place occupied by the mechanics is the high value placed on their service in early time.[1222] In like manner the trumpeters (tubicines, liticines) and the hornblowers (cornicines) were grouped each in a century for voting in the comitia,[1223] also on the basis of their guild organizations.[1224] The accensi velati, who as we are informed followed the army in civilian dress and without weapons,[1225] also received a centuriate organization. As to the number of centuries belonging to them opinion has differed. Some, formerly including Mommsen,[1226] have assumed two. Livy,[1227] however, gives but one century; Cicero[1228] seems to have only one in mind; and in imperial time there was a single collegium, or century, of accensi,[1229] probably a survival of the old political group. These