Section 13-353. Retirement; for accident disability

Medical examination of a
  member  in city-service for accident disability and investigation of all
  statements and certifications by him or her or on his or her  behalf  in
  connection   therewith  shall  be  made  upon  the  application  of  the
  commissioner, or upon the application of a member or of a person  acting
  in his or her behalf, stating that such member is physically or mentally
  incapacitated  for  the  performance  of  city-service, as a natural and
  proximate result of such city-service, and certifying  the  time,  place
  and  conditions  of such city-service performed by such member resulting
  in such alleged disability and that such alleged disability was not  the
  result  of  wilful  negligence  on the part of such member and that such
  member should, therefore, be retired. If such  medical  examination  and
  investigation   shows   that  such  member  is  physically  or  mentally
  incapacitated for the performance  of  city-service  as  a  natural  and
  proximate  result  of an accidental injury received in such city-service
  while a member, and that such disability was not the  result  of  wilful
  negligence  on  the  part  of such member and that such member should be
  retired, the medical board shall so certify to the  board,  stating  the
  time, place and conditions of such city-service performed by such member
  resulting  in  such  disability, and such board shall retire such member
  for accident disability forthwith.