In chapter 22, we are introduced to lexicon.org/place/great-britain/england/london/st-mungos-hospital/">St Mungo’s hospital. But we are also introduced to two other new ideas, one of which remained a mystery to fans even after the last book was published. One of these new ideas is the fact that the portraits of previous headmasters and headmistresses of Hogwarts are not actually asleep but act as advisers to the current head. It’s kind of surprising to realize that we didn’t learn that fact until book five! It seems so much a part of the world of Hogwarts that it feels like we knew it all along. The other interesting new idea is the dual smoke snakes emitted from the silver instrument in Dumbledore’s office and the mysterious phrase “In essence divided.” We can trace the point in the stories where Rowling started answering all the questions and solving all the mysteries, and that happened with the publication of the sixth book. Here she’s still in the stage of creating questions rather than answering them, of laying out clues for her readers to puzzle over. And this puzzle was a doozy. It doesn’t seem all that mysterious now, of course, since we know about Horcruxes and the concept of splitting one’s soul. But when book five came out, we had no hint of that. So we had no framework within which to interpret Dumbledore’s musings. What was divided? The snake? Harry? Was Harry part snake, and was that somehow related to his ability to speak lexicon.org/thing/parselmouth/">Parseltongue? Were there two snakes — and although it seems laughable now, was the lexicon.org/place/great-britain/england/surrey/zoo/reptile-house/">boa constrictor from book one somehow related to the venomous snake that accompanied Voldemort? Fans puzzled over this for years. In fact, even after book seven came out, fans still wondered just what exactly those words and that smoke image meant. Rowling was asked about it in an interview and she explained it as follows: Dumbledore suspected that the snake’s essence was divided – that it contained part of Voldemort’s soul, and that was why it was so very adept at doing his bidding. This also explained why Harry, the last and unintended Horcrux, could see so clearly through the snake’s eyes, just as he regularly sees through Voldemort’s. Dumbledore is thinking aloud here, edging towards the truth with the help of the Pensieve. (lexicon.org/source/interviews/blc/">BLC) Okay, so it wasn’t actually the Pensieve that showed Dumbledore the image of the snakes, but no matter. Rowling went into even more detail about Horcruxes in another post-Deathly Hallows interview, and here she even brings up the concept of a piece of a person’s soul longing and striving to rejoin what she calls the Master Soul. Here’s what she said: Well, of course, the pain he feels whenever Voldemort is particularly active, is this piece of soul seeking to rejoin the Master Soul. When his scar is hurting him so much, that’s not scar tissue hurting him. That’s this piece of soul really wanting to get back out the way it entered. … It entered this boy’s body through a wound and it wants to rejoin the Master Soul when Voldemort’s near him, when he’s particularly active … That’s what I always imagined this pain was … There’s a moment when Dumbledore casts a charm and you see a two-headed snake split. It’s in Dumbledore’s office, and he suddenly … performs this strange piece of magic in which he watches images … this snake dividing and that’s the way he sees Voldemort’s soul dividing. He’s playing through his own theory about what’s happened and his theory, is of course, correct. That Voldemort [is], as summed up by the snake, divided.