The significance of extravascular coagulation and fibrinolysis is poorly understood and little appre-ciated. A unique opportunityfor studying these events is provided in arthritis where the joint fluids may reflect the presence and extent of inflammation. This report on 144 pathological fluids expands our knowledge of the biochemistry of inflammation. Further, it may provide a more instructive base than currently available for comprehending the mechanisms operative in arthritis. Fibrin deposition must be considered seriously as a contributor to permanent joint damage.

Synovial fluid isa complex mixture of substances largely derived from the plasma but also the product and recipient of both cells in the synovial membrane and extravascular leucocytes (Ropes and Bauer, 1953). Protein comprises 1* 4 to 5* 6 per cent. of the synovial fluid and is mainly knownin terms of electrophoretic properties (Decker, McKenzie, McGuckin, and Slocumb, 1959; Schur and Sandson, 1963; Schmid, 1964) except for rheumatoid factor (Krehl, Boisvert, de Forest, and Mucci, 1957) and several enzymes (Ziff, Simson, Scull, Smith, Shatton, and Mainland, 1955; Jacox and Feldmahn, 1955; Smith and Hamerman, 1962). There is little quantitative information on specific proteins. We selected globulins that function in fibrin formation and degradation for measurement as they are constituents of inflammation fluids but are considered absent in synovial fluid (Ropes and Bauer, 1953; Cho and Neuhaus, 1960). When present with cellular products, activation may occur to yield or destroy fibrin (Seegers, 1962; Barnhart, 1963; Purcell and Barnhart, 1963).