Pictures Of The Capillaries Fridge Thermostat Broken. How Does It Work?

Fridge thermostat broken. How does it work? - pictures of the capillaries

I looked in my fridge and saw that the thermostat is broken metal capillary fridge / freezer in two. I mean thin metal tube that is glued to the bottom of the freezer sense temperature.

Here's a picture: (paste into your browser) coldsupply.com/true/800306.jpg

Is there a gas through the metal tube? Why is it hollow? The end came out that was closed crowned.