var imageFiles_by_13 = new Array();
imageFiles_by_13['0'] = new Array ('_images/by_Goose_Necks.gif', '_images/by_Goose_NecksMouseover.gif');

function image_on_by_13 (position) {
   var doc = eval("document.imageby_13" + position);
   doc.src = imageFiles_by_13[position][1];
}

function image_off_by_13 (position) {
   var doc = eval("document.imageby_13" + position);
   doc.src = imageFiles_by_13[position][0];
}