I came across that quotation in Schopenhauer's The World as Will and Presentation, in his discussion of human beauty. Schopenhauer has also an interesting note on human form and a suggestion it contains, stressed in some art. "Even in the higher animals the head and the trunk are still much more one thing than in the human being, whose head appears as if freely set upon the body, only borne by it, not serving it. This prerogative of the human is displayed to the highest degree by the Apollo of Belvedere: the head of the god of the Muses stands on his shoulders, gazing so freely far and wide that it appears as if it is wrenched entirely away from the body, no longer a servant to concern for it"(209).