Should any endowment be made either by donation, inter vivos or mortis causa, to establish a professorship in any institution of learning in the State, duly incorporated, on the principal being deposited in the State treasury, the same shall be invested, and the interest as realized shall be paid over as stipulated in La. Rev. Stat. 17:2231, and it shall be the duty of the Auditor of Public Accounts and the State Treasurer to make the investments to the greatest advantage and interest of said institution.