Constitutional Amendment - Declares that Congress may by law provide for the case of death or inability of Members of the House of Representatives, and the case of inability of Members of the Senate, in the event that one-fourth of either House is killed or incapacitated, declaring who shall serve until the disability is removed or a new Member is elected. Terminates such procedures within 120 days after the death or inability of one-fourth of the House or Senate. Allows extensions of additional 120-day periods if one-fourth of either the House or Senate remains vacant or occupied by members unable to serve.