…we reckon only the Skull and the Brain… Both these aspects are mentioned in both Idras – the Idra Rabba and Idra Zuta. The Idra Rabba speaks only of the Skull and the Brain within it (mentioning the Cavity only as the membrane of the concealed brain), while specifying in detail all the repairs instituted in the hairs and nose, explaining each institution individually in full (see Idra Rabba p. 128b). On the other hand the Idra Zuta mentions Three Heads and does not speak at any length about the repairs, making only brief reference to them in order to bring them under the overall premise discussed there. (Idra Zuta p. 288a, and see Etz Chayim, Shaar Arich Anpin ch. 3: “the Three Heads include the Cavity”.)