We will deal first with the publicani.
In a passage of Livy quoted just now it is stated that at the beginning of the Hannibalic war money was advanced to the State by societates publicanorum; Livy also happens to mention that three of these competed for the privilege.

Thus it is clear that the system of getting public work done by contract was in full operation before that date, together with the practice on the part of the contractors of uniting in partnerships to lessen the risk.

System and practice are equally natural, and it needs but a little historical imagination to realise their development.

As the Roman State became involved in wars leading to the conquest of Italy, and in due time to the acquisition of dominions beyond sea, armies and fleets had to be equipped and provisioned, roads had to be made, public rents to be got in, new buildings to be erected for public convenience or worship, corn had to be procured for the growing population, and, above all, taxes had to be collected both in Italy and in the provinces as these were severally acquired.[111] The government had no apparatus for carrying out these undertakings itself; it had not, as we have, separate departments or bureaux with a permanent staff of officials attached to each, and even if it had been so provided, it would still have found it most convenient, as modern governments also do, to get the necessary work carried out in most cases by private contractors.

Every five years the censors let the various works by auction to contracting companies, who engaged to carry them out for fixed sums, and make what profit they could out of the business (_censoria locatio_).