307. Persons claiming under the mortgagor.

The following persons claiming under the mortgagor can redeem:

  1.  

    (1)     an assignee of the equity of redemption, including a volunteer1;

  2.  

    (2)     a subsequent incumbrancer2;

  3.  

    (3)     a tenant for years under a lease made subsequent to the mortgage which the mortgagee refuses to confirm3; and

  4.  

    (4)     a surety on payment by himself or refusal by the principal debtor to discharge the mortgage debt, or if the surety has mortgaged his own estate as security for the debt