Section 13-123. Medical board

a. (1) There shall be a medical board of three
  physicians.  One  of such physicians shall be appointed by the board and
  shall hold office at the pleasure of such board, one shall be  appointed
  by  the  commissioner of health and shall hold office at the pleasure of
  such commissioner, and the third shall be appointed by the  commissioner
  of  citywide  administrative  services  and  shall  hold  office  at the
  pleasure of such commissioner.
    (2) The board, the commissioner of  health  and  the  commissioner  of
  citywide administrative services shall each have power to appoint one or
  more  but not exceeding four alternate physicians, who shall hold office
  at the pleasure of such appointing board or official. Whenever the board
  of trustees of the retirement system shall  so  direct,  the  functions,
  powers  and  duties of the medical board, in addition to being performed
  and exercised by the three physicians appointed  pursuant  to  paragraph
  one of this subdivision, shall be performed and exercised by one or more
  groups of three physicians as hereinafter prescribed. Each such group of
  three physicians shall function separately as the medical board and each
  such  group  may  consist  partly of a physician or physicians appointed
  pursuant to paragraph one of this subdivision and partly of one or  more
  alternate  physicians  or  may consist entirely of alternate physicians;
  provided, however, that one of the physicians or alternate physicians in
  each such group shall be appointed by the board, one by the commissioner
  of health  and  one  by  the  commissioner  of  citywide  administrative
  services.
    b. The medical board shall arrange for and shall pass upon all medical
  examinations   required  under  the  provisions  of  this  title,  shall
  investigate all essential statements and certifications by or on  behalf
  of a member in connection with an application for disability retirement,
  and  shall  report  to  the  board  its  conclusions and recommendations
  thereon.