Another of the wonderful, imaginative anatomy preparations from the Horniman Museum. This is one of the series of animals (bat, hedgehog, rabbit) which appears to have been prepared by grabbing it by the feet on the right hand side, and dipping it half way into fierce acid until everything is gone but the bone. Sort of like cooking a doughnut on only one side (see 1 min 34 secs into this useful video).
Of course this ISN'T how this preparation was made. I'm only guessing here, but I think the steps involved:
1. Catch a Hedgehog. Decide not to eat it, but kill it anyway.
2. Carefully slice down the belly, flip hedgehog inside out
3. Gut and otherwise remove innards
4. Dissolve off the last nasty bits to leave a nice clean skeleton
5. Meanwhile clean the skin, halve it (!!) and tan for taxidermy
6. Complete the Haynes' five spanner difficulty rating reassembly of the hedgehog bones
7. Recombine, ensuring that the skeleton toes fit back into the skin perfectly!
This apparently is called a skeletal mount. I think that is an understatement of the sheer genius of imagining creating this weird work of genius.