Collision damage and GUIHealth script not working

Hello - Will,
My script is unfortunately not working, no errors, just not working, written myself.

var Health = 100;
var healthcount : Transform;
var Enemy : Transform;
var healthText;
var Damage = 10;

 function Start()
 {
 healthText = healthcount.transform.GetComponent.<TextMesh>();
 }
 

function OnCollionEnter(other : Collision){
     if (other.GameObject.tag == "Enemy"){
     	Health = Health - Damage;
     }
     if (Health <= 0)
     {
     	Application.LoadLevel(Application.loadedlevel);
     }
}


function Update()
{
healthText.text = Health.ToString();
}

Do you have a rigidbody on one of your colliding objects? Are the tags set up correctly? Have you linked up all your public references in the inspector? The code looks okay but looks likely to be an issue with setup like the points I have just mentioned.