var firstImage = 0;
var prevImage = images.length - 1;
var nextImage = 1;
var lastImage = images.length - 1;

function changeImage (x) {

	document.images.ImageBox.src = images[x];
	document.getElementById("ImageCaptionBox").innerHTML= captions[x];

	firstImage = 0;
	lastImage = images.length - 1;

	if (x > 0) {
		prevImage = x - 1;
	} else {
		prevImage = images.length - 1;
	}

	if (x < (images.length - 1)) {
		nextImage = x + 1;
	} else {
		nextImage = 0;
	}

}