Prototype: call method from another method

I’m using the Prototype JS library to make classes.

var myClass = Class.create({
   initialize: function() {
      this.myValue = 5;
   returnHello: function() {
      return 'hello';
   explainYourself: function() {
      return this.returnHello() + ", my value is: " + this.myValue;

In explainYourself(), I tried to call returnHello() and I got an error saying this.returnHello() is not a function. What is the correct syntax?

And how do you make field and methods private/public/protected in Prototype?