Two orthogonal 'hourglasses' moving relative to each other [Deux 'sabliers' orthogonaux se mouvant l'un par rapport a l'autre].
When looking at this picture and moving the head forward and backward, the two orthogonal 'hourglasses' structures seem to move relative to each other.
(CMAP28 WWW site: this page was created on 08/30/2024 and last updated on 08/31/2024 14:27:24 -CEST-)