Development of the articular space demonstrated in the elbow joint of mice embryos]

Development of the articular space demonstrated in the elbow joint of mice embryos The development of the elbow-joint of mice (day 12–19 p. c.) was investigated by means of light- and electron-microscopy. The cartilage-anlagen, which are separated by a wide interzone, appear on day 12 p. c. in the homogenous blastema of the limb-bud. The cells of the interzone have numerous mutual contacts thereby causing the development of an uniform cell-clone which synthesizes and secretes a special intercellular substance rich in hyaluronate. Cartilage contact is avoided by this means and the beginning of movements in this waterrich layer become possible. This interzone disappears during later development. The first sign of the joint space can be seen on day 17 p. c. The joint surfaces smooth out before birth and the synovial fluid is seen by electron-microscope. Two directions of differentiation of the mesen-chyme of the interzone and the cartilage are discussed.