Ad Dig. 28,5,69Windscheid: Lehrbuch des Pandektenrechts, 7. Aufl. 1891, Bd. I, § 93, Note 4.The Same, On Quintus Mucius, Book VII. A certain man appointed Sempronius his heir under the following condition: “If Titius should ascend to the Capitol.” Even though Sempronius could not become the heir unless Titius should ascend to the Capitol, and this absolutely depends upon the inclination of Titius, for the reason that the desire of Titius is not expressly referred to in the will the appointment will be valid. But if the testator had said, “If Titius is willing, let Sempronius be my heir”; the appointment would be void. For certain things which are mentioned in wills have no force or effect, if, when they are obscured by words, they have the same signification as if they had been expressed, and have a certain amount of weight; for instance, the disinheritance of a son will be valid where there is an heir, and still no one doubts that if a testator should disinherit his son as follows: “Let Titius be my heir, and when he is my heir, let my son be disinherited”; that a disinheritance of this kind if of no force whatever.