9 To a stranger, or a child above the age of puberty whom a man has
instituted heir, he cannot appoint a substitute to succeed him if he
take and die within a certain time: he has only the power to bind him by
a trust to convey the inheritance to another either wholly or in part;
the law relating to which subject will be explained in its proper place.

TITLE XVII. OF THE MODES IN WHICH WILLS BECOME VOID

A duly executed testament remains valid until either revoked or
rescinded.

1 A will is revoked when, though the civil condition of the testator
remains unaltered, the legal force of the will itself is destroyed, as
happens when, after making his will, a man adopts as his son either an
independent person, in which case the adoption is effected by imperial
decree, or a person already in power, when it is done through the agency
of the praetor according to our constitution. In both these cases the
will is revoked, precisely as it would be by the subsequent birth of a
family heir.

2 Again, a subsequent will duly executed is a revocation of a prior
will, and it makes no difference whether an heir ever actually takes
under it or not; the only question is whether one might conceivably have
done so. Accordingly, whether the person instituted declines to be heir,
or dies in the lifetime of the testator, or after his death but before
accepting the inheritance, or is excluded by failure of the condition
under which he was instituted--in all the cases the testator dies
intestate; for the earlier will is revoked by the later one, and the
later one is inoperative, as no heir takes under it.

3 If, after duly making one will, a man executes a second one which is
equally valid, the Emperors Severus and Antoninus decided by rescript
that the first is revoked by the second, even though the heir instituted
in the second is instituted to certain things only. The terms of this
enactment we have ordered to be inserted here, because it contains
another provision. 'The Emperors Severus and Antoninus to Cocceius
Campanus. A second will, although the heir named therein be instituted
to certain things only, is just as valid as if no mention of the things
had been made: but the heir is bound to content himself with the things
given him, or with such further portion of the inheritance as will make
up the fourth part to which he is entitled under the lex Falcidia, and
(subject thereto) to transfer the inheritance to the persons instit