Any idea why my int wont display on GUI

using UnityEngine;
using System.Collections;

public class player_health : MonoBehaviour {

	public int health = 100;				// setup player health and default value
	
	
	// Update is called once per frame
	void FixedUpdate () {
		Debug.Log ("PLayer Health : " + health);		// display player health (for debugging)
		if (health==0)
		Application.LoadLevel("Death Screen");
	}
	
	
	
	public void Increase_Health (int amount)		// a function that takes an integer as a parameter and adds this amount from player health
	{
		health = health + amount;
	}
	
	
	
	public void Decrease_Health (int amount)     // a function that takes an integer as a parameter and subtracts this amount from player health
	{
		health = health - amount;  // This is the function that damage_player is using, giving damage to as 'amount'
	}
	

	void onGUI()
	{
		GUI.Label (new Rect (400, 25, 500, 125), string.Format("{0}", "Health =" + health));	//This displays the health value on the screen.
	}
}

I am unsure why the int ‘health’ will not be displayed, I have tried many different methods of displaying it with OnGUI, none have worked, so there must be something I am missing, so I would appreciate a fresh pair of eyes to help me out finding my problem.

It’s OnGUI not onGUI ^^