nav_locations_off = new Image();
nav_locations_off.src = "/images/nav_locations_off.png";
nav_locations_on = new Image();
nav_locations_on.src = "/images/nav_locations_on.png";

nav_disorders_off = new Image();
nav_disorders_off.src = "/images/nav_disorders_off.png";
nav_disorders_on = new Image();
nav_disorders_on.src = "/images/nav_disorders_on.png";

nav_studies_off = new Image();
nav_studies_off.src = "/images/nav_studies_off.png";
nav_studies_on = new Image();
nav_studies_on.src = "/images/nav_studies_on.png";

function imageon(imagename) {
	imgOn = eval(imagename + "_on.src");
	document[imagename].src = imgOn;
}

function imageoff(imagename) {
	imgOff = eval(imagename + "_off.src");
	document[imagename].src = imgOff;
}