javascript still not quite working

I spliced this together from found code and creative trial and error. Logically I'm pretty sure it should work, but there are some peices I don't quite understand...


first I set up arrays of the images and captions for each slideshow:

var original_img = new Array();
original_img[1] = "images/original/original.jpg";
original_img[2] = "images/original/astoria.jpg";
original_img[3] = "images/original/alisasausage1.jpg";
original_img[4] = "images/original/marysausage1.jpg";
original_img[5] = "images/original/hotdogmary.jpg";

var original_cap = new Array();
original_cap[1] = "Amy and the Infamous Roast Beef Dinner";
original_cap[2] = "Astoria, Queens";
original_cap[3] = "Alisa";
original_cap[4] = "Mary";
original_cap[5] = "HOT DOG";

var garlic_img = new Array();
garlic_img[1] = "images/original/original.jpg";
garlic_img[2] = "images/original/astoria.jpg";
garlic_img[3] = "images/original/alisasausage1.jpg";

var garlic_cap = new Array();
garlic_cap[1] = "Amy and the Infamous Roast Beef Dinner";
garlic_cap[2] = "Astoria, Queens";
garlic_cap[3] = "Alisa";


these functions are supposed to make the clicked-on slideshow the array used for the slideshow function then call the slideshow function:

var Picture = new Array();
var Caption = new Array();


function getShow1() {
var Picture = original_img.slice();
var Caption = original_cap.slice();
//alert (Caption[1]);
runSlideShow();
}

function getShow2() {


runSlideShow();
}

function getShow3() {


runSlideShow();
}

function getShow4() {


runSlideShow();
}

slideshow function:

var current=1

function runSlideShow(){
document.getElementById("media_image").setAttribute("src", Picture[current]);
document.getElementById("media_caption").innerHTML= Caption[current];
current=(current setInterval("runSlideShow()", 2500);
}

in the html (disassembled or else blogger tries to load it):

links to slideshows:
a href="#" onclick="getShow1()">the beginning
a href="#" onclick="getShow2()">meat platter
a href="#" onclick="getShow3()">garlic

where displayed:
img src="1.jpg" name="media_image" id="media_image" width=450 height=400
div class="basic_text" id="media_caption"