Event.observe 
(
 	window,
	'load',
	function ()
	{
		var menuItems = $$ ('.swappable');
		
		menuItems.each
		(
		 	function (item)
			{
				var targetImage = item;
				
				var mouseOutImageSrc = targetImage.src;
				var mouseOverImageSrc = targetImage.src.sub ('.jpg', '-over.jpg');
				
				var image = new Image ();
				image.src = mouseOverImageSrc;
				
				Event.observe 
				(
					targetImage,
					'mouseover',
					function ()
					{
						targetImage.src = mouseOverImageSrc;
					}
				);
				
				Event.observe 
				(
					targetImage,
					'mouseout',
					function ()
					{
						targetImage.src = mouseOutImageSrc;
					}
				);
			}
		);
	}
);