These classes are (a) where the mortgagor binds himself to repay the mortgage money : (b) where, by any cause other than the wrongful act or default of the mortgagor or mortgagee, the mortgaged property is wholly or partially 645 destroyed or the security is rendered insufficient within the meaning of section 66, and the mortgagee has given the mortgagor a reasonable opportunity of providing further security enough to render the whole security sufficient, and the mortgagor has failed to do so ; (c) where the mortgagee is deprived of the whole or part of his security by or in consequence of the wrongful act or default of the mortgagor ; (d) where the mortgagee being entitled to possession of the mortgaged property, the mortgagor fails to deliver the same to him, or to secure the possession thereof to him without disturbance by the mortgagor or any person claiming under a title superior to that of the mortgagor.