//subnavi init:
submenu1_lo = new Image();
submenu1_hi = new Image();
submenu2_lo = new Image();
submenu2_hi = new Image();
submenu3_lo = new Image();
submenu3_hi = new Image();
submenu4_lo = new Image();
submenu4_hi = new Image();

submenu1_lo.src = "img/navis/sub_case_contents_lo.gif";
submenu1_hi.src = "img/navis/sub_case_contents_hi.gif";
submenu2_lo.src = "img/navis/sub_case_present_lo.gif";
submenu2_hi.src = "img/navis/sub_case_present_hi.gif";
submenu3_lo.src = "img/navis/sub_case_practice_lo.gif";
submenu3_hi.src = "img/navis/sub_case_practice_hi.gif";
submenu4_lo.src = "img/navis/sub_case_diagnosis_lo.gif";
submenu4_hi.src = "img/navis/sub_case_diagnosis_hi.gif";