EXHIBIT 4 AMENDMENT NO. 3 TO RIGHTS AGREEMENT This Amendment No. 3 to the Preferred Shares Rights Agreement, dated June 4, 1999 ("Amendment"), amends that certain Preferred Shares Rights Agreement (the "Rights Agreement"), dated as of August 21, 1996...Preferred Shares Rights Agreement • June 7th, 1999 • Metra Biosystems Inc • In vitro & in vivo diagnostic substances • California
