In this variety the bones are connected by a disc of fibro-cartilage, and possess just as much movement as the flexibility and compressibility of the joining substance allows. Mixed joints have no smooth surfaces or synovial capsules. Examples of this description of joint are found in the union of the bodies of the vertebrae (fig. 346), where a pad of elastic fibro-cartilage exists and gives to the spine as a whole its flexibility and springiness without permitting undue mobility between each pair of vertebrae.