if (document.images) {
   
   image27on = new Image();
   image27on.src = "../images/ttl_sub_hist_1.gif";
   
   image28on = new Image();
   image28on.src = "../images/ttl_sub_hist1_1.gif";
   
   image29on = new Image();
   image29on.src = "../images/ttl_sub_hist2_1.gif";
   
   image30on = new Image();
   image30on.src = "../images/ttl_sub_hist3_1.gif";
   
   image27off = new Image();
   image27off.src = "../images/ttl_sub_hist_0.gif";
   
   image28off = new Image();
   image28off.src = "../images/ttl_sub_hist1_0.gif";
   
   image29off = new Image();
   image29off.src = "../images/ttl_sub_hist2_0.gif";
   
   image30off = new Image();
   image30off.src = "../images/ttl_sub_hist3_0.gif";
   
}

function turnOn(imageName) {
  if (document.images) {
    document[imageName].src = eval(imageName + "on.src");
  }
}

function turnOff(imageName) {
  if (document.images) {
    document[imageName].src = eval(imageName + "off.src");
  }
}

// -->