The following requisites are essential to the contracts of pledge and mortgage:
(1) That they be constituted to secure the fulfillment of a principal obligation;
(2) That the pledgor or mortgagor be the absolute owner of the thing pledged or mortgaged;
(3) That the persons constituting the pledge or mortgage have the free disposal of their property, and in the absence thereof, that they be legally authorized for the purpose.
Third persons who are not parties to the principal obligation may secure the latter by pledging or mortgaging their own property. (1857)