[MARCIANUS libro quarto institutionum. ] §28.6.36.prPotest quis in testamento plures gradus heredum facere, puta: 'si ille heres non erit, ille heres esto', et deinceps plures, ut nouissimo loco in subsidium uel seruum necessarium heredem instituat.
[MARCIANUS, from the fourth book of Institutions.] Anyone can establish several degrees of heirs in a will, for example: "If that person is not the heir, let the other person be the heir," and thereafter successively more, so that in the last place, as a reserve, he may even appoint a slave as a necessary heir.
§28.6.36.1Et uel plures in unius locum possunt substitui uel unus in plurium uel singulis singuli uel inuicem ipsi qui heredes instituti sunt.
And either several can be substituted in the place of one, or one in the place of several, or individual substitutes for individual heirs, or reciprocally those very persons who have been appointed heirs.