triking ability, if not the most complicated technically The bones of the skull come from two sources a specialized layer of embryonic cells called the mesenchyme differentiates either into cartilage, which is replaced by bone, or into a thick, tough membrane also replaced by bone Replacement of membrane is not complete in the normal human until the sixth year Face dancers received injections shortly after birth that slowed and eventually stopped ossification and stimulated replacement of the membrane by musclelike tissue Later localized mjec ttons reversed the cartilage to bone process in limited areas These areas softened into cartilage cells called chondrocytes enclosing masses of disconnected chondrocytes and organic salts In place of certain facial bones then, the face dancer had envelopes of elas Uc cartilage filled with material of a puttylike consistency This specialized cartilage also replaced the normal material of the nose and ears During the years before puberty exercises allowing for the differential stimulation of the muscles of the face were performed daily Of course, these exercises were not unique to face dancers the Fremen woman Harah was known to have been disturbed at the sight of Aha bitting and staring at a rock, moving only one muscle beside her nose (P Oulson, St Alia Huntress of a Billion Worlds Ch 7) an indication of a Bene Gessent regimen of the same kind By mas tery of these muscles the face dancer changed such things as the size and shape of his "cheekbones as easily and quickly as one might smile For longer-lasting disguises the face dancer working from likenesses of the victim, would mold the matter within the cartilage envelopes to the desired form which would then be retained indefinitely barring some trauma or unusual exertion of the facial muscles The muscles that replaced the membranes between the large bones of the vault of the skull could be manipulated to increase or FACE DANCERS 209 FACE DANCERS decrease the size of the skull within narrow limits, or to change somewhat the shape of the skull Varying Hair and Eye Color The muscle covered fontanelies in the skull also indirectly permitted the change of hair color Cellular manipulation of the embryo created an m creased branching of the vertebral artery Several small extensions of this artery through the fontanelies supplemented the normal flow of blood to the scalp Early face dancers made use of the time-honored methods of hair dyes and wigs, but later master face dancers could increase the temperature of the scalp through a range of 4 C by consciously varying the supply of blood These masters had no natural hair on then* scalps, instead, each follicle was implanted with a strand containing a liquid crystal which responded to changes in temperature by changing color The temperature-sensitive pat was implanted deep in the skull to protect it from ambient temperature changes The method was almost a thousand years m development early mas