MeshRegion seems to function quite differently from any other Mathematica expression. One cannot take a
Part of it. Nor can I simply exchange its head to something else using
Apply. What is going on here and how do I extract the argument in some manipulable form?
MeshRegion is an atomic expression. This may be to allow an optimized internal form. See an explanation for why
Graph is atomic in Why is Graph an atomic expression in Mathematica?. Parts can be taken using
Options. (I do not know whether these three functions can obtain all data contained in a MeshRegion but for now it seems like it.)
Another workaround would be to convert to a
String and act on that:
However, this might be a bad idea since there is a reason why Mathematica tries to keep us from taking arguments like this.