Section 3121. Physical or mental examination

(a) Notice of examination.
  After commencement  of  an  action  in  which  the  mental  or  physical
  condition or the blood relationship of a party, or of an agent, employee
  or  person  in  the custody or under the legal control of a party, is in
  controversy, any party may serve notice on another party to submit to  a
  physical,  mental  or blood examination by a designated physician, or to
  produce for such examination his agent, employee or the  person  in  his
  custody or under his legal control. The notice may require duly executed
  and  acknowledged  written  authorizations  permitting  all  parties  to
  obtain, and make copies of, the records of specified hospitals  relating
  to  such  mental  or  physical  condition or blood relationship; where a
  party  obtains  a  copy  of  a  hospital  record  as  a  result  of  the
  authorization of another party, he shall deliver a duplicate of the copy
  to  such party. A copy of the notice shall be served on the person to be
  examined. It shall specify the time, which shall be not less than twenty
  days after service of the notice, and the conditions and  scope  of  the
  examination.
    (b)  Copy  of  report.  A  copy  of  a  detailed written report of the
  examining physician setting out his findings and  conclusions  shall  be
  delivered  by  the party seeking the examination to any party requesting
  to exchange therefor a  copy  of  each  report  in  his  control  of  an
  examination  made  with  respect  to the mental or physical condition in
  controversy.