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                                                                    EXHIBIT 24.2


                          GELTEX PHARMACEUTICALS, INC.

                            Certificate of Secretary

         I, Peter Wirth, being the duly elected and acting Secretary of GelTex
Pharmaceuticals, Inc. (the "Company"), a Delaware corporation, hereby certify
that the following is a true, correct and complete copy of resolutions duly
adopted by the Board of Directors of the Company by unanimous written consent
dated March 28, 1996; and that said resolutions have not been amended or
rescinded and are now in full force and effect.

         Registration Statement on Form S-8

         VOTED:   That the President, any Vice President and the Treasurer of
                  the Company, each acting singly, are hereby authorized in the
                  name and on behalf of the Company to execute and file with the
                  Commission a registration statement on Form S-8 (the
                  "Registration Statement") relating to the registration under
                  the Securities Act of 1933, as amended (the "Act"), of 75,000
                  shares of the Company's Common Stock reserved for issuance
                  under the Company's 1995 Director Stock Option Plan, such
                  Registration Statement and any amendments thereto to be in
                  such form as may be approved by the officer executing the
                  same, his execution and filing thereof to be conclusive
                  evidence of this approval; and take any and all other action
                  as they or any of them may deem necessary or advisable to
                  effect such registration.

         VOTED:   That any officer of the Company executing, on behalf of the
                  Company or in any other capacity, the Registration Statement
                  and any and all amendments to such Registration Statement and
                  other documents to be filed with the Commission in connection
                  therewith is hereby authorized to execute the same through or
                  by Mark Skaletsky or Peter Wirth, as attorney-in-fact,
                  pursuant to a power of attorney reflecting such authorization.

         WITNESS my signature and the seal of the Company affixed this 24th day
of June, 1996.

[CORPORATE SEAL]                            /s/ Peter Wirth
                                            ------------------------------------
                                            Peter Wirth, Secretary


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