Where does jell-o come from?

Gelatine seems benign enough. And in fact it is. It's nothing but molecules of protein that have been heated and then, as they cool, trap tiny particles of water. But where does that protein come from? The rumors are always spoken of in hushed terms: that Jello is made of horse hooves... or worse. Actually the truth is worse. Or at least it sounds worse. The source of the protein in Jell-O is "hide trimmings," animal tissue that is rendered, purified, filtered, and then purified again, leaving a protein called collagen. Of course, then they have to go and ruin their exposition with gratitous veggie-bashing: The gelatin that is the building block of Jell-O is so purified that the FDA doesn't regard it as a meat product. Likewise, all but the strictest vegetarians find Jelly acceptable. Gee, thanks. What does the FDA know, anyway?