EXHIBIT 3.21


                           CERTIFICATE OF AMENDMENT

                                    OF THE

                         CERTIFICATE OF INCORPORATION

                                      OF

                   S & W X-Ray OF ROCHESTER, NEW YORK, INC.

                           Under Section 805 of the
                           Business Corporation Law


     The undersigned, being the president and secretary of S & W X-Ray of
Rochester, New York, Inc., hereby certify as follows:

     1.   Name
          ----

          The name of the corporation is S & W X-Ray of Rochester, New York,
Inc.  The name under which the corporation was formed was S & W X-Ray of
Rochester, New York, Inc.

     2.   Date of Filling of the Certificate of Incorporation
          ---------------------------------------------------

          Its Certificate of Incorporation was filed by the Department of State
on April 26, 1973.

     3.   Amendments
          ----------

          The Certificate of Incorporation as now in full force and effect is
amended, as authorized by Sections 801 and 805 of the Business Corporation Law,
to effect the following amendments:  to change the name of the corporation to S
& W X-Ray, Inc.; and to change the total number of shares which the corporation
is authorized to issue from 200 common shares without par value to 500,000
common shares having a par value of $.04 per share, and to change shares,
thereby reducing stated capital.

     4.   Text of Amendments
          ------------------

          Paragraphs 1 and 3, which refer respectively to the name of the
corporation and to the number of shares that may be issued, are amended to read
as follows:

          1.   The name of the corporation shall be:  S & W X-Ray, Inc.

 
          3.   The aggregate number of shares which the corporation shall have
authority to issue is 500,000 shares, all of which are to be common shares
having a par value of $.04 per share.

          5.   Change of Issued Shares
               -----------------------

               The number of issued shares changed is 100 common shares without
par value. The 100 issued shares shall be changed into 250,000 issued common
shares having a par value of $.04 per share, at the rate of 2,500 shares for
each share presently issued.

          6.   Change of Unissued Shares
               -------------------------

               The number of unissued shares changed is 100 common shares
without par value. The 100 unissued shares shall be changed into 250,000
unissued common shares having a par value of $.04 per share, at the rate of
2,500 shares for each share presently unissued.

          7.   Reduction of Stated Capital
               ---------------------------

               The stated capital of the corporation is reduced from $28,000 to
$20,000 by a change of shares under subparagraph (b)(11) of Section 801 of the
Business Corporation Law.

          8.   Authorization
               -------------

               This amendment to the Certificate of Incorporation was authorized
by a vote of the board of directors followed by a vote of the holders of a
majority of all of the outstanding shares entitled to vote thereon at a meeting
of the shareholders.

          IN WITNESS WHEREOF, we have signed this Certificate of Amendment this
14th day of February, 1992.
                                                                                

                                        /s/ Bruce Ashby             President
                                        ---------------------------
                                        Bruce Ashby



                                        /s/ Joseph S. Miller, Jr.   Secretary
                                        ----------------------------            
                                        Joseph E. Miller, Jr.

                                      -2-

 
STATE OF NEW YORK   )
COUNTY OF MONROE    )    SS.


     Joseph E. Miller, Jr., being duly sworn, deposes and says that he is the
secretary of the corporation named in the foregoing Certificate of Amendment;
that he has read and signed the same; and that the statements contained therein
are true.


                                              /s/ Joseph E. Miller, Jr.
                                              ---------------------------------
                                              Joseph E. Miller, Jr.


Sworn to before me this
14 day of February, 1992.
- --        --------       

/s/ Roxann Gendron
- ----------------------------

 
                         CERTIFICATE OF CHANGE OF THE

                        CERTIFICATE OF INCORPORATION OF

                   S & W X-RAY OF ROCHESTER, NEW YORK, INC.

              Under Section 805-A of the Business Corporation Law

IT IS HEREBY CERTIFIED THAT:

     (1)  The name of the corporation is:

            S & W X-RAY OF ROCHESTER, NEW YORK, INC.

     (2)  The certificate of incorporation was filed by the Department of State
on the 26th day of April, 1973.

     (3)  The certificate of incorporation is changed as follows:

     Paragraph Five (5) of the Certificate of Incorporation is hereby amended to
reflect the following changes:

     The Secretary of State is designated as agent of the Corporation upon whom
process against it may be served.  The post office address to which the
Secretary of State shall mail a copy of any process against the Corporation
served upon him is:

                              c/o  The Corporation
                                   72 Marway Circle
                                   Rochester, NY  14624

     (4)  The change to the Certificate of Incorporation was authorized by a
vote of the Board of Director(s), followed by a vote of the holder(s) of a
majority of all outstanding shares entitled to vote thereon at a meeting of
shareholders.

 
IN WITNESS WHEREOF, this certificate has been subscribed this 25th day of 8,
                                                              ----        - 
1988 by the undersigned who affirm that the statements made herein are true
- ----                                                                       
under the penalties of perjury.

Bruce Ashby, President/Secretary         /s/ Bruce Ashby
- --------------------------------         -------------------------

Joseph E. Miller, Jr.,, V-Pres./Trea.    /s/ Joseph S. Miller, Jr.
- -------------------------------------    -------------------------

 
        CERTIFICATE OF AMENDMENT OF THE CERTIFICATE OF INCORPORATION OF

                    S & W X-RAY OF ROCHESTER, NEW YORK, INC.
               under Section 805 of the Business Corporation Law

IT IS HEREBY CERTIFIED THAT:

     (1)  The name of the corporation is:

                    S & W X-Ray of Rochester, New York, Inc.

     (2)  The certificate of incorporation was filed by the department of state
on the 26th day of April, 1973.

     (3)  The certificate of incorporation is hereby amended to effect the
          following change:

          Paragraphs "5" and "6" of the Certificate of Incorporation dealing
          with the address of the corporation shall be amended to read as
          follows:

               5.   The office of the corporation is to be located at 1322
                    Buffalo Road, Town of Gates, County of Monroe and State of
                    New York, 14624.

               6.   The Secretary of State of the State of New York is
                    designated as agent of the Corporation upon whom process
                    against it may be served. The post office address to which
                    the Secretary of State shall mail a copy of any process
                    against the Corporation served upon him is:

                                   c/o The Corporation
                                   72 Marway Circle
                                   Rochester, NY  14624

 
     (4) The amendment to the certificate of incorporation was authorized:

          * [at a meeting of shareholders by vote of a majority of all the
            outstanding shares entitled to vote thereon.]

          * by unanimous written consent of the holders of all the outstanding
            shares entitled to vote thereon.

          * [at a meeting of shareholders by vote of
            all outstanding shares entitled to vote thereon as required by the
            certificate of] incorporation.

          * by the sole in[corporate for the reason that no shares have been
            issued, no directors or officers have been elected, and there are no
            subscribers for shares whose subscriptions have been accepted.]

*        STRIKE OUT WHERE INAPPLICABLE

 
IN WITNESS WHEREOF, this certificate has been subscribed this 22nd day of 2,
                                                              ----        - 
1983 by the undersigned who affirm(s) that the statements made herein are true
under the penalties of perjury.



 
      Type Name      Capacity in which signed     Signature
      ---------      ------------------------     ---------
                                            
     Bruce Ashby           President          /s/ Bruce Ashby
     Keith Ashby           Secretary          /s/ Keith Ashby


 
                          CERTIFICATE OF INCORPORATION

                                       OF

                    S & W X-Ray OF ROCHESTER, NEW YORK, INC.

                         PURSUANT TO SECTION 402 OF THE
                            BUSINESS CORPORATION LAW

     We, the undersigned, in order to form and organize a corporation under the
Business Corporation law of the State of New York, do hereby make, execute, and
present to the Department of State of said State, for filing pursuant to Law,
the following Certificate of Incorporation:

     1.   The name of the corporation shall be The undersigned, being the
president and secretary of S & W X-Ray of Rochester, New York, Inc.

     2.   The purposes for which it is to be formed are to do any all of the
things hereafter set forth to the same extent as natural persons might or could
do in any part of the world namely:

     To conduct and carry on the business of engaging in the purchase and sale
of radiographic chemicals and equipment.  To purchase and sell all types of
photographic chemistry.  To buy, to sell and purchase all types of photographic
and radiographic film processors.  To buy, sell and install photographic and x-
ray accessories and to buy and sell photographic film.

     To purchase, lease or otherwise acquire, and to hold, own, sell, dispose of
real and personal property of all kinds and in particular lands, buildings,
business concerns and undertakings, share of street mortgages, bonds,
debentures, and securities, merchandise, book debts and claim, trade marks,
trade names, and any interest in real or personal property.

 
     To sell, improve, manage, develop, lease, mortgage, dispose or to otherwise
turn to account or deal with all or any part of the property of the corporation.

     3.   The total number of shares of stock that may be issued is Two Hundred
(200), all of which are to be without par value.

     4.   The share of stock shall be all common stock with equal voting powers
and privileges.

     5.   The office of the corporation is to be located at 150 Garford Road, in
the City of Rochester, County of Monroe and State of New York 14622.

     6.   The Secretary of State of the State of New York is hereby designated
as agent of the corporation upon whom process against it may served, and the
Post Office Address to which the Secretary of State shall mail a copy of any
process against it served upon him is 150 Garford Road, in the City of
Rochester, County of Monroe, and State of New York, 14622.

                                      -2-

 
     IN WITNESS WHEREOF, We, being over twenty-one years of age, have made,
signed, and acknowledged this certificate this 23rd day of March, 1973.
                                               ----                    

                                               /s/ Keith Ashby
                                               ---------------------------------
                                               KEITH E. ASHBY
                                               150 Garford Road
                                               Rochester, New York 14622

                                               /s/ Bruce P. Ashby
                                               ---------------------------------
                                               BRUCE P. ASHBY
                                               150 Garford Road
                                               Rochester, New York 14622

STATE OF NEW YORK   )
COUNTY OF MONROE    )    SS.
TOWN OF PENFIELD    )

     On this 23rd day of March, 1973, before me personally came Keith E. Ashby,
             ----                                                              
to me known and known to me to be the same person described in and who executed
the foregoing certificate of incorporation, and that he duly acknowledged to me
that he executed the same.

                                               /s/ Donald J. Mark
                                               --------------------------------

                                               Comm. of Deeds
                                               --------------------------------

STATE OF NEW YORK   )
COUNTY OF MONROE    )    SS.
TOWN OF PENFIELD    )

     On this 23rd day of March, 1973, before me personally came Bruce Ashby, to
             ----                                                              
me known and known to me to be the same person described in and who executed the
foregoing certificate of incorporation, and that he duly acknowledged to me that
he executed the same.

                                               /s/ Donald J. Mark
                                               --------------------------------

                                               Comm. of Deeds
                                               --------------------------------

                                      -3-