Yellow elastic tissue is found nearly pure in the ligamentum nuchae, and tunica abdominis, the coats of the largest arteries and elsewhere. The lungs contain a large quantity of this tissue. When white fibrous tissue is boiled gelatine is obtained, which is not the result of boiling the yellow elastic tissue. ADIPOSE TISSUE.--Fat or adipose tissue consists of cells containing an oily material, and arranged in isolated groups, or slightly separated by meshes of areolar tissue. It is found in many parts of the body, and varies greatly in quantity; in joints it occurs between the ligaments, and serves the purpose of a packing material, while in the form of medulla or marrow it occupies the cavities of bones. In fat cell a nucleus is very rarely visible. LIGAMENTS.--Ligaments are dense, fibrous, connecting structures. They exist in most articulations, and are made up principally of white fibrous tissue. There are two kinds--capsular or bursal, and funicular or binding ligaments. Capsular ligaments are membranous structures enclosing true joints. They consist of a dense interlacement of fibers attached to bones, round the edges of the articular cartilages; some regard them as a continuation of the periosteum or the covering of bone. They are never closely applied, their use being to form cavities round the joints, enclosing and protecting the synovial or lubricating apparatus inside. Funicular or binding ligaments consist of rounded or flattened cords, or bands of fibrous tissue, passing from one bone to another, firmly attached to roughened portions of their surfaces. They hold the bones in their places, at the same time allowing the requisite amount of motion in the joints. Ligaments which are situated between bones are often termed interosseous. Annular ligaments are those which bind down and protect the tendons of muscles in certain joints, converting grooves in the bones into channels or tubes which are lined with synovial membrane, and through which the tendons play. Some ligaments are composed almost entirely of yellow elastic tissue, such as the ligamentum nuchae (the elastic ligament of the neck) and the ligaments connecting the vertebral arches (arches between the bones of the spinal column). SYNOVIAL MEMBRANES.--These are thin membranes lining the capsular ligaments of joints, or they are interposed elsewhere between structures which move one upon another, and which would otherwise be injured by the friction. Near the borders of articular cartilages the membrane is generally found as a projecting fold, the projection being due to a small pad of fat, interposed between the membrane and the capsular ligament. These projections were once erroneously termed synovial glands, but their use is probably to assist in forcing the synovia between the opposing surfaces of cartilage.