Part 13 · Chapter 73

And since the membrane, which is the Tifferet, always inclines to the Hesed, and it is also a branch of the Daat hidden in the air, therefore it is called the membrane of the air [Kruma deAvira] and not the membrane of the brain. And since in the air the Daat of Atik clothes, which is not included in the seven lower [Sefirot] of Atik but is their soul [Neshama], therefore only the seven corrections of the Rosh were mentioned and they did not say the eight corrections of the Rosh, for the air does not enter into their category, because it is hidden.