Whenever any loan is called in and the borrower shall fail to pay the principal and interest due to the association as required by law and the notices given him, the land mortgage association may then foreclose upon the mortgaged premises as for a past-due loan. But in no case shall a borrower be liable for a sum greater than the amount of the unpaid portion of the loan with any accretions of interest thereon and expenses incidental to the collection thereof. (1925, c. 223, s. 13.)