Where can I find the "Animate Physics" option (tick box) within the Animator component in Inspector?

I have a model called "Girl" with Animator component:

However, it seems to be missing an option called "Animate Physics" which is demonstrated in this Unity Tutorial: https://www.youtube.com/watch?v=Xx21y9eJq1U (at 5:39) , and here is the screenshot of it:

I'm currently using Unity version 4.5.3f.3, and I'm wondering, could the missing option be caused by simply that the updated version has removed this option from the inspector, or have I got some Unity setting incorrectly?