CERTIFICATE OF INCORPORATION

                                       of

                                 MRL NuCor, Inc.


                              ---------------------


FIRST, the name of the corporation is

                                 MRL NuCor, Inc.


SECOND,  the  address  of the  corporation's  registered  office in the State of
Delaware is 1209 Orange Street, in the City of Wilmington, County of New Castle.
The  name of the  Registered  Agent at such  address  is The  Corporation  Trust
Company.

THIRD, the purpose of the corporation is (i) to acquire, own, operate, maintain,
provide,  furnish  and  generally  deal in and  with,  in any  lawful  capacity,
pathology  and  clinical   laboratories,   pathology  and  clinical   laboratory
facilities,   services,   techniques,   establishments  and  equipment  for  the
observation,  analysis and evaluation of materials, fluids, tissue and organisms
of every kind and  description;  (ii) to carry on any other  business  as may be
necessary,  convenient, or desirable to accomplish the above purposes; and (iii)
generally to engage in any lawful act or activity for which  corporations may be
organized under the General Corporation Law of the State of Delaware.



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FOURTH, the total number of shares of all classes of stock which the corporation
shall have  authority to issue is 3,000 shares which shall be Common Stock,  all
of which shares shall be without par value, and each with a right to one vote.

FIFTH, the name and mailing address of the Incorporator are as follows:

         Name                               Mailing Address

         Bruce G. Goodman                   80 Wilson Way
                                            Westwood, Massachusetts 02090


SIXTH, (a) No director of the corporation  shall have any personal  liability to
the corporation or its stockholders for monetary damages for breach of fiduciary
duty as a director,  provided that this  provision  shall not eliminate or limit
the liability of a director (i) for any breach of the director's duty of loyalty
to the corporation or its  stockholders,  (ii) for acts or omissions not in good
faith or which involve  intentional  misconduct  or a knowing  violation of law,
(iii) under Section 174 of the General Corporation Law of the State of Delaware,
or (iv) for any transaction from which the director derived an improper personal
benefit.
         (b) Each person who was or is made a party or is  threatened to be made
a party to or is involved  in any action,  suit or  proceeding,  whether  civil,
criminal,  administrative  or  investigative  (hereinafter a  "proceeding"),  by
reason  of the fact  that he or she,  or a person of whom he or she is the legal
representative,  is or was a director or officer of the corporation or is or was
serving at the request of the  corporation as a director,  officer,  employee or
agent of another corporation or of a partnership,  joint venture, trust or other
enterprise,  including  service with respect to employee benefit plans,  whether
the basis of such


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proceeding  is alleged  action in an official  capacity as a director,  officer,
employee or agent or in any other capacity while serving as a director, officer,
employee or agent,  shall be indemnified and held harmless by the corporation to
the fullest  extent  authorized by the General  Corporation  Law of the State of
Delaware,  as the same exists or may  hereafter be amended  (but, in the case of
any  such  amendment,  only  to the  extent  that  such  amendment  permits  the
corporation to provide  broader  indemnification  rights than said law permitted
the  corporation  to provide  prior to such  amendment),  against all  expenses,
liability and loss (including  attorneys' fees,  judgments,  fines, excise taxes
pursuant to the Employee  Retirement Income Security Act of 1974, as amended, or
penalties and amounts paid or to be paid in settlement)  reasonably  incurred or
suffered by such person in connection therewith and such  indemnification  shall
continue  as to a person who has ceased to be a director,  officer,  employee or
agent  and  shall  inure  to the  benefit  of his or her  heirs,  executors  and
administrators;  provided,  however,  that, the corporation  shall indemnify any
such person  seeking  indemnification  in connection  with a proceeding (or part
thereof)  initiated by such person only if such proceeding (or part thereof) was
authorized  by the  Board  of  Directors  of the  corporation.  The  right to be
indemnified  conferred  in this  Article 6 shall be a  contract  right and shall
include  the  right  to be paid by the  corporation  the  expenses  incurred  in
defending  any such  proceeding in advance of its final  disposition;  provided,
however, that, if the General Corporation Law of the State of Delaware requires,
the payment of such  expenses  incurred by the director or officer in his or her
capacity  as a  director  or  officer  (and not in any other  capacity  in which
service was or is to be  rendered  by such  person  while a director or officer,
including, without limitation, service to an employee benefit


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plan), in advance of the final  disposition of a proceeding,  shall be made only
upon  delivery to the  corporation  of an  undertaking,  by or on behalf of such
director or officer,  to repay all amounts so advanced if it shall ultimately be
determined that such director or officer is not entitled to be indemnified under
this Article or  otherwise.  The  corporation  may, by action of its  directors,
provide indemnification to employees and agents of the corporation with the same
scope and effect as the foregoing indemnification of directors and officers.
         (c) The  indemnification  provided by this Article 6 shall not limit or
exclude any rights,  indemnities or limitations of liability to which any person
may  be  entitled,  whether  as a  matter  of  law,  under  the  By-Laws  of the
corporation,  by agreement,  vote of the stockholders or disinterested directors
of the corporation or otherwise.
         (d) The corporation may maintain insurance,  at its expense, to protect
itself  and any  director,  officer,  employee  or agent of the  corporation  or
another  corporation,  partnership,  joint  venture,  trust or other  enterprise
against any such  expense,  liability  or loss,  whether or not the  corporation
would have the power to indemnify such person against such expense, liability or
loss under the General Corporation Law of the State of Delaware.

SEVENTH,  any action  required or permitted to be taken at any annual or special
meeting  of  stockholders  of the  corporation  may be taken  without a meeting,
without prior notice and without a vote, if a consent in writing,  setting forth
the actions so taken, shall be signed by the holders of outstanding stock having
not less than the minimum  number of votes that would be  necessary to authorize
or take such action at a meeting at which all shares  entitled  to vote  thereon
are present and voted.


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THE UNDERSIGNED, being the sole Incorporator hereinbefore named, for the purpose
of forming a corporation pursuant to the General Corporation Law of the State of
Delaware, does hereby make this Certificate,  declaring and certifying that this
is his act and deed and the facts herein stated are true,  and  accordingly  has
hereunto set his hand this 5th day of October, 1994.


                                             /s/ Bruce G. Goodman
                                             ------------------------
                                             Bruce G. Goodman
                                             80 Wilson Way
                                             Westwood, Massachusetts  02090




COMMONWEALTH OF MASSACHUSETTS  )
                               ) ss
COUNTY OF NORFOLK              )


         BE IT  REMEMBERED,  that on this 5th day of October,  1994,  personally
came before me, a Notary Public in and for the Commonwealth of Massachusetts and
the County of Norfolk,  Bruce G.  Goodman,  the sole  Incorporator  named in the
foregoing  Certificate of Incorporation,  known to me personally to be such, and
he acknowledged  the said  Certificate to be his act and deed and that the facts
stated therein are truly set forth.


                                             GIVEN under my hand seal of 
                                             office the day and year aforesaid.


                                             /s/ Bruce G. Goodman
                                             ------------------------


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                            CERTIFICATE OF AMENDMENT

                                       OF

                          CERTIFICATE OF INCORPORATION
                            (Pursuant to Section 242)
                                      *****


         MRL NuCor,  Inc., a  corporation  organized  and existing  under and by
virtue of the General Corporation Law of the State of Delaware,
         DOES HEREBY CERTIFY:

         FIRST:  that  the  Board  of  Directors  of  said  corporation,  by the
unanimous  written consent of its members,  filed with the minutes of the Board,
adopted a resolution  proposing and declaring  advisable the following amendment
to the Certificate of Incorporation of said corporation:

         RESOLVED,  that the Certificate of Incorporation of MRL NuCor,  Inc. be
         amended by changing the First Article thereof so that, as amended, said
         Article shall be and read as follows;

              "FIRST, the name of the corporation is Corning MRL, Inc."

         IN WITNESS WHEREOF,  said corporation has caused this certificate to be
signed by Bruce G. Goodman, its Assistant Secretary,  this 28th day of December,
1994.
                                                   MRL NUCOR, INC.



                                                   By:/s/ Bruce G. Goodman
                                                      ---------------------
                                                   Its: Assistant Secretary





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