img1on = new Image();
	img1on.src = "images/aliphatic_button-on.gif";
	img2on = new Image();
	img2on.src = "images/olefin_button-on.gif";
	img3on = new Image();
	img3on.src = "images/aromatic_button-on.gif";
	
	img1off = new Image();
	img1off.src = "images/aliphatic_button-off.gif";
	img2off = new Image();
	img2off.src = "images/olefin_button-off.gif";
	img3off = new Image();
	img3off.src = "images/aromatic_button-off.gif";	



function bmouseDown(imgName) {
	document[imgName].src = eval(imgName + "on.src");
}

function bmouseUp(imgName) {
	document[imgName].src = eval(imgName + "off.src");
}