Spine controller

I've managed to follow the next few pages in the book and ended up with a spine thats controlled by an IK Spline. Using the Hypershade, i've added a multiply divide node and a condition node which has been plugged into each joint apart from the last. I've also entered a bit of Mel script to generate and arc length node (arclen -ch on BindSpineSIKCurve;) which has also been plugged into the multiply and condition nodes.

I have absolutely no idea what i've just done, or why i've done it - just followed the instructions, which defeats the whole point of the process.

The two handles i created using the cv curve tool and snapping it around various points on a cylinder.