Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
The proposal,
which the consul Quintus Caepio seventeen years after the introduction
of the equestrian tribunals (648) brought in for again entrusting the
trials to senatorial jurymen, showed what the government wished; but
showed also how little it could do, when the question was one not
of squandering domains but of carrying a measure in the face of
an influential order. It broke down.(5)
The government was not
emancipated from the inconvenient associates who shared its power;
but these measures probably contributed still further to disturb the
never sincere agreement of the ruling aristocracy with the merchant-
class and the proletariate. Both were very well aware, that the
senate granted all its concessions only from fear and with reluctance;
permanently attached to the rule of the senate by considerations
neither of gratitude nor of interest, both were very ready to render
similar services to any other master who offered them more or even as
much, and had no objection, if an opportunity occurred, to cheat or
to thwart the senate.