Paul Irish 'duck punching' pattern question
<p>Had a question about the 'duck punching' pattern I first encountered on Paul Irish's blog.  I get the general premise... save a ref to an existing  function, then replace the existing function with a conditional branch that will call a new function if condition is met, or the old version if not.  My question is why do we have to use the "apply" with 'this' as the first param when we call the _old function?  I understand how apply works, but I'm looking for some clarification on why it is necessary.  </p>

<pre><code>(function($){

        // store original reference to the method
        var _old = $.fn.method;

        $.fn.method = function(arg1,arg2){

            if ( ... condition ... ) {
               return  .... 
            } else {           // do the default
               return _old.apply(this,arguments);
            }
        };
    })(jQuery);
</code></pre>
