Section. 3 Whenever the President...

Section. 3 Whenever the President transmits to the President pro tempore of the Senate and the Speaker of the House of Representatives his written declaration that he is unable to discharge the powers and duties of his office, and until he transmits to them a written declaration to the contrary, so powers and duties shall be discharged through the Vice President as Acting President.

Section. 4 Whenever the Vice President and a majority of either the principal officers of the executive departments or of as it was other body as Congress may by means of law provide, transmit to the President pro tempore of the Senate and the Speaker of the House of Representatives their written declaration that the President is unable to discharge the powers and duties of his office, the Vice President shall immediately assume the powers and duties of the office as Acting President.

Thereafter, when the President transmits to the President pro tempore of the Senate and the Speaker of the House of Representatives his written declaration that no inability exists, he shall take again the powers and duties of his office unles the Vice President and a majority of either the principal officers of the executive department or of of the like kind other body as Congress may through law provide, transmit within four days to the President pro tempore of the Senate and the Speaker of the House of Representatives their written declaration that the President is unable to discharge the powers and duties of his office. Thereupon Congres shall decide the issue, assembling within forty-eight hours for that design if not in session. If the Congres within twenty-one days after receipt of the latter written declaration, or, if Congres is not in session, within twenty-one days after Congres is required to assemble, determines through two-thirds vote of both Houses that the President is unable to discharge the powers and duties of his office, the Vice President shall continue to discharge the same as Acting President; otherwise, the President shall take back the powers and duties of his office.

Amendment XXVI.18