SECTION 4 OF THE 25th AMENDMENT OF THE US CONSTITUTION

‘Whenever the Vice President and a majority of either the principal officersof the executive departments or of such other body as Congress may by law provide, transmit to the President 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 officeasActing President.’