(From per, and a joint).
A moveable articulation; abarticutatio, and dearti-tulatio. Different authors vary in their division; but Dr. Hunter supposes it to consist of three species: 1st, The enarthrosis, or ball and socket; when a large head is received into a deep cavity, as the head of the femur into the acetabulum of the os innominatum: its synonym is genou. 2dly, Arthrodia; when a round head is received into a superficial cavity: these two kinds admit of a motion on all sides. 3dly, The ginglymus, called also cardo, cardinamentum; because it resembles the motion of a hinge. There are properly but two species of this articulation; the first confined to flexion and extension, the angular ginglymus, where each bone receives partly, and partly is received by the other, as in the articulation of the humerus with the ulna, or where the joint is adapted only to small turns towards each side, the lateral ginglymus. This last is either single, as in the articulation of the first vertebra of the neck, with the apophysis dentiformis of the second; or double, that is, in two different parts of the bone, as in the articulation of the ulna with the radius.