The foregoing statement of the slave's various activities, apart from peculium, would be very misleading unless it were borne in mind that a slave, in any way engaged in commerce, had, as a matter almost of course, a peculium: it was the existence of this which made it more or less safe to deal with him. In essence the peculium was a fund which masters allowed slaves to hold and, within limits, to deal with as owners. It was distinct from the master's ordinary property—the patrimonium, and though in law the property of the master, it is constantly spoken of as, de facto, the property of the slave. It is an aggregate of res peculiares, which belong to the master, and of which the slave is administrator. It is described as pusillum patrimonium, and velut patrimonium proprium. We are concerned with it as it was in classical and later law, but it may be well to premise a few remarks as to its earlier history.

(1) At first it seems to have been unimportant and to have consisted merely of small savings on allowances, and unexpended balances on authorised transactions. But by the beginning of the Empire, it might be of great value, and of any form. It might include other slaves, (one in the peculium of another slave being called a vicarius,) and the peculia of vicarii (even vicarii vicaricrum), land, inheritances, obligations and so forth. The vicarius might indeed be more valuable than the principal slave. It might thus reach a very large amount.