Exercised over material commodities
or slaves, it has become _dominium_--over children, it is
_Potestas_--over free persons whose services have been made away to
another by their own ancestor, it is _mancipium_--over a wife, it is
still _manus_. The old word, it will be perceived, has not altogether
fallen into desuetude, but is confined to one very special exercise
of the authority it had formerly denoted. This example will enable us
to comprehend the nature of the historical alliance between Contracts
and Conveyances. There seems to have been one solemn ceremonial at
first for all solemn transactions, and its name at Rome appears to
have been _nexum_. Precisely the same forms which were in use when a
conveyance of property was effected seem to have been employed in the
making of a contract. But we have not very far to move onwards before
we come to a period at which the notion of a Contract has disengaged
itself from the notion of a Conveyance. A double change has thus taken
place. The transaction "with the copper and the balance," when
intended to have for its office the transfer of property, is known by
the new and special name of Mancipation. The ancient Nexum still
designates the same ceremony, but only when it is employed for the
special purpose of solemnising a contract.

When two or three legal conceptions are spoken of as anciently blended
in one, it is not intended to imply that some one of the included
notions may not be older than the others, or, when those others have
been formed, may not greatly predominate over and take precedence over
them. The reason why one legal conception continues so long to cover
several conceptions, and one technical phrase to do instead of
several, is doubtless that practical changes are accomplished in the
law of primitive societies long before men see occasion to notice or
name them. Though I have said that Patriarchal Power was not at first
distinguished according to the objects over which it was exercised, I
feel sure that Power over Children was the root of the old conception
of Power; and I cannot doubt that the earliest use of the Nexum, and
the one primarily regarded by those who resorted to it, was to give
proper solemnity to the alienation of property. It is likely that a
very slight perversion of the Nexum from its original functions first
gave rise to its employment in Contracts, and that the very slightness
of the change long prevented its being appreciated or notic