Recursively Calling A Function Within A Class Definition

i've got an object and i'd like to recursively call a function
within the class definition.

(i've simplified the code )

function myclass()
{
this.loop = function(index)
{
// ..work

setTimeout( "loop(" + (index+1) + ")", 100 );
}
}

does not work.

i've also tried

setTimeout( function() { loop(index+1) }, 100 );

i've also prefixed this. to loop in both cases - and no workee.

i think it's some sort of scope problem.