11 EXHIBIT H AGREEMENT TO FILE JOINTLY We, the undersigned, hereby express our agreement that the attached Schedule 13D is filed on behalf of each of us.

                                                                11
                                   EXHIBIT H

                           AGREEMENT TO FILE JOINTLY

     We, the undersigned, hereby express our agreement that the attached
Schedule 13D is filed on behalf of each of us.

                                        HOECHST CORPORATION



Date:  October 28, 1996                 By:  /s/ Xxxxx X Xxxxxxx
                                             Xxxxx X. Xxxxxxx
                                             Vice President, General
                                             Counsel and Secretary


                                        HOECHST XXXXXX XXXXXXX, INC.



Date:  October 28, 1996                 By:  /s/ Xxxxxxx X. Xxxxxxx
                                             Vice President,
                                             General Counsel, and
                                             Corporate Secretary