jqery function wont work

Hi, Why cant the following jquery work when I place the code in a separate function as below

I get no error but no animation.

$(document).ready(function(){
 
  var $val1=6;
  var $val2=10.3;
  var img = ["images/bcave1.png", "images/bcave2.png"];
  var indexNum=0;
  
	setInterval("animatepic1()",100);
 /*  var gameLoop = setInterval( function(){
	  $("#pic").attr("src", img[indexNum]);
      indexNum++;	
      if (indexNum >= 2) {indexNum = 0;} 
	   
	   } , 100);
	   */
  
 
   
 }); 
 
   function animatepic1(){
			 $("#pic").attr("src", img[indexNum]);
     		 indexNum++;	
      		 if (indexNum >= 2) {indexNum = 0;} 
	   
	    }

.....
<img id ="pic" src="images/bcave1.png" alt="eight ball" />

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