Creepy-crawlies and the impurity of them leads to the question of what happens if you eat portion of the creepy-crawly, and not its entirety? (in terms of impurity, not kashrut). Plus, the apparent "souls" of the creatures. Also, R. Akiva is at odds with the sages (though he comes around eventually) for 6 ways if being impure (or not, if you're the sages). Plus, a story of a box of bones which didn't have enough of the key bones from one person to render another impure. [Who's Who: Todros the doctor] Plus, the importance of the spine and the skull.