num_spans = 5;
text_span = new makeArray(num_spans - 1);

text_span[0].text_id = 'airplane_text';
text_span[0].img_id = 'airplane_img';
text_span[0].img_highlight_src = 'images/airplane_s.jpg';
text_span[0].img_src = 'images/airplane_s_g.jpg';

text_span[1].text_id = 'waveguide_text';
text_span[1].img_id = 'waveguide_img';
text_span[1].img_highlight_src = 'images/waveguide_s.jpg';
text_span[1].img_src = 'images/waveguide_s_g.jpg';

text_span[2].text_id = 'dalton_text';
text_span[2].img_id = 'dalton_img';
text_span[2].img_highlight_src = 'images/dalton_s.jpg';
text_span[2].img_src = 'images/dalton_s_g.jpg';

text_span[3].text_id = 'dendrimer_text';
text_span[3].img_id = 'dendrimer_img';
text_span[3].img_highlight_src = 'images/dendrimer_s.jpg';
text_span[3].img_src = 'images/dendrimer_s_g.jpg';

text_span[4].text_id = 'chb_text';
text_span[4].img_id = 'chb_img';
text_span[4].img_highlight_src = 'images/chb_s.jpg';
text_span[4].img_src = 'images/chb_s_g.jpg';


function makeArray(n)
{
        this.length = n;
        for (var i = 0; i <= n; i++)
        {
            this[i] = new Image();
        }
        return this;
}

function close_all_spans()
{
	for (var i = 0; i < (num_spans); i++)
	{
		document.all[text_span[i].text_id].style.display = "none";
		document.images[text_span[i].img_id].src = text_span[i].img_src;
	}
}

function highlight(span_label, id)
{
	close_all_spans();
	document.all[span_label].style.display = "block";
	document.images[text_span[id].img_id].src = text_span[id].img_highlight_src;
}