XII. On the Words in Psalm cxxxix. 15 : “My Substance or (Bones) Was Not Hid from Thee, Which Thou Madest in Secret.” It is said also by those who treat of the nature and generation of animals, that the change of the blood into bone is something invisible and intangible, although in the case of other parts, I mean the flesh and nerves, the mode of their formation may be seen. And the Scripture also, in Ecclesiastes, adduces this, saying, “As thou knowest not the bones in the womb of her that is with child, so thou shalt not know the works of God.” 1392 But from Thee was not hid even my substance, as it was originally in the lowest parts of the earth. 1392     Eccles. xi. 5 .