Problem with load->model()

[eluser]Unknown[/eluser]
Hy everybody. I'm novice in CI and I'm making a site to train. The site works very well with Ajax and JQuery, but I want load the pages from a database instead of a file '.php'. To this I insert the CI on production. I was following the help pages but I had a problem with the function load->model.

I want that the work on this way: I click on menu link, the JQuery sends a ajax request to 'index.php/layout/ajax/' + hash (where hash is the page to load), the controller layout.php loads the model and returns to JQuery the page requested. The problem starts here, because I think that the CI will make a object with my load->model('Ajax_model) but the return is this:

class Ajax_model extends CI_Model { function Ajax_model() { parent::Model(); } function get($page) { $query = $this->db->query( 'SELECT content FROM pages WHERE pagename="' . $page . '"' ); return $query->result(); } }
Fatal error: Class 'Ajax_model' not found in C:\xampp\htdocs\mySite\system\core\Loader.php on line 303

Code:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Layout extends CI_Controller {

public function index()
{
  $this->load->helper('url');
  //the data array will be filled with database calls
  $this->load->view('layout',
   $data = array(
    'title' => 'NoLimits',
    'siteName' => 'NoLimits',
    'slogan' => 'Helping You Grow Your Business',
    'defaultPage' => 'home'
   )
  );
}
public function ajax()
{
  $page = $this->uri->segment($this->uri->total_segments());
  
  $this->load->model("Ajax_model", "ajax", TRUE);
  $this->ajax->get_page($page);
}
}

/* End of file layout.php */
/* Location: ./application/controllers/layout.php */

Code:

class Ajax_model extends CI_Model {

    function __construct()
    {
        parent::__construct();
    }

function getPage($page)
{
        $query = $this->db->query(
   'SELECT content
   FROM pages
   WHERE pagename="' . $page . '"'
  );
        return $query->result();
}
}
/* End of file ajax_model.php */
/* Location: ./application/models/ajax_model.php */

I'm crazing about this. Sugestions is extremely welcome.
(Sorry by my bad english)

PS: My CodeIgniter is 2.1.0