When a proprietor has died or shall have died infeft in lands, and the heir of the investiture has expede or shall have expede a general service as heir of such proprietor, the decree of general service in favour of such heir shall be equivalent to a mortis causa general disposition of the lands by such proprietor in favour of such heir, to the effect of enabling such heir, or those deriving right from or by succession to him, to expede and record in the appropriate register of sasines all notarial instruments applicable to such lands which a general disponee or .those deriving right from him may expede and record under or in terms of " The Titles to Land Consolidation (Scotland) Act, 1868," or of this Act, and that notwithstanding that such proprietor may have died in nonage or been of insane mind, or laboured under any other disability whatever ; provided always, that no general service shall have such effect in any case where the heir so served shall have died before the commencement of this Act; and a general service expede by the heir of any person so 'served and dying after the commencement of this Act, or by any of the successive heirs of the investiture, or by the heir of any general disponee, shall have the like effect as a transmission of the right to the lands ; and any such services shall be sufficient links in the series of titles for the connection of the person expeding such instrument with the person last infeft, in the same manner as is herein-before provided with reference to two or more general dispositions forming links in such series.