Is bone in bone china?

Excuse me, I'm curious about a rather unusual topic. Could you possibly clarify for me if bone china actually contains bone? I've heard varying rumors about this traditional English tableware, some claiming it's purely ceramic while others insist it incorporates bone ash. I'm quite fascinated by the craftsmanship and the potential scientific underpinnings behind it. If bone china does incorporate bone, what is the purpose of this addition? Does it improve the strength, durability, or aesthetic qualities of the finished product? I'd appreciate any insights you could offer on this intriguing subject.