For the next eight years (99-91) Rome enjoyed a season of comparative quiet. CHAPTER XXIV. INTERNAL HISTORY.-THE SOCIAL WAR (90-88). At this time there was a bitter rivalry between the Senate and the equestrian order, or commercial class. From the former were chosen the governors of the provinces, from the latter came the tax-gatherers (_publicani_) and the money-brokers (_negotiatores_). It will help us to understand better the condition of affairs, if we study the composition of the Senate and the Equites. The Senators, three hundred in number (later their number was increased to six hundred), held their office for life. When vacancies occurred from death, or occasionally from removal, they were filled by the Censor, (Footnote: See the duties of Censor) who appointed a person that had held one of the following offices: Dictator, Consul, Praetor, Curule Aedile, or, after the time of Sulla, Quaestor. All persons who had held these offices, or that of Tribune, were allowed to join in debate in the Senate, but not to vote. No Senator could engage in business. Hence he must be wealthy. We saw in Chapter IV. that Roman citizens were divided into six classes according to their property, and that these classes were subdivided into one hundred and ninety-three other classes called centuries. About 225, the number was increased to three hundred and seventy-three. Eighteen of the centuries of the first class were called EQUITES, and must have property worth twenty thousand dollars or more. This name was given to them because at first they served in the army as horsemen, though in later times the cavalry was composed only of allied troops. The Equites were originally from the aristocracy alone, but, as the plebeians increased in wealth, many of them became rich enough to be included in this class.