Hello guys, i have start working with CodeIgniter, but i can't understand one think. How do i load one class into another?

$this->load->library("hello_world");

This is not working?

my class -> load -> hello_world class

class myclass {
      function test() {
         $this->load->library("hello_world");
         $this->hello_world->hello();
      }
}

Message: Undefined property: myclass::$load