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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 a resolution duly
adopted by the Board of Directors of the Company by unanimous written consent
dated July 19, 1996; and that said resolution has not been amended or rescinded
and is now in full force and effect.


         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 19th day
of July, 1996.



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