PUBLIC LAWS-CH. 512-AUG. 7, 1947 Detail of officers of the line. Officers of Medical Service and Nurse Corps. Detail of officers of the line. Restriction. Appointment of boards, etc. Rear admiral. of the Nurse Corps, shall consist of not less than six nor more than nine officers of the corps concerned above the grade of commander. (2) The officers composing these boards shall be officers on the active or retired list of the Navy. In case there be not a sufficient number of officers of the corps concerned legally or physically capacitated to serve on a selection board of such corps, officers of the line on the active list of equivalent rank may be detailed to duty on such board to constitute the required minimum membership. (3) Boards for the recommendation of officers of the Medical Serv- ice Corps and of the Nurse Corps for temporary promotion to grades above lieutenant (junior grade) shall be composed of not less than six nor more than nine officers above the grade of commander on the active or retired list of the Medical Corps: Provided That in case there be not a sufficient number of officers of the Medical Corps legally or physically capacitated to serve on such a selection board, officers of the line of the active list of the grade of captain may be detailed to duty on such board to constitute the required minimum membership. (4) No officer may be a member of two successive selection boards for the consideration of officers for promotion to the same grade, or for the consideration of officers for continuation on the active list in the same grade. (5) The boards prescribed in subsection (b) of this section shall be appointed by the Secretary of the Navy and convened at least once each year at a time as soon as practicable after the report of a corre- sponding board for the selection of line officers has been approved by the President, and at such times as the Secretary of the Navy may direct: Provided, That a selection board to recommend officers of the Medical Service Corps for temporary promotion to the grade of cap- tain or officers of the Nurse Corps for temporary promotion to the grade of commander or lieutenant commander shall be convened only if there exists a vacancy in the grade concerned or if the Secretary of the Navy estimates or determines that a vacancy will occur in the ensuing twelve-month period. OATH FOR MEMBERS OF SELECTION BOARDS SEc. 306. Each member of a board provided for in section 305 of this title shall swear, or affirm, that he will, without prejudice or partiality, and having in view both the special fitness of officers and the efficiency of the naval service, perform the duties imposed upon him as herein provided. ELIGIBILITY OF OFFICERS FOR CONSIDERATION BY SELECTION BOARDS SEC. 307. (a) The following provision shall relate to line officers: (1) Rear admirals, not restricted in the performance of duty, who, subsequent to June 30 of the fiscal year preceding that in which the first selection board is convened pursuant to this title to recommend officers of that grade for continuation on the active list, attain the status of having completed four years of service in grade and thirty- four years of total commissioned service, shall become eligible for consideration for such recommendation by such board convened in the fiscal year in which they first attain such status: Provided, That a rear admiral who shall have lost numbers or precedence at any time shall become eligible for such consideration in the fiscal year in which the most senior rear admiral junior to him who has not lost numbers or precedence becomes eligible therefor: Provided further, That such eligibility shall continue until the officer concerned shall have been selected for continuation on the active list or until he shall have twice failed of such selection, whichever shall occur earlier. 842 [61 STAT.