Some properties of human and other synovial fluids.

The main object of this paper is to report measurements made on a small series of human synovial fluids and on a few sheep and ox fluids. These measurements were made in order to test the two methods suggested by Ogston & Stanier (1953 a) for detecting differences of the specific properties of the hyaluronic acid as it occurs in synovial fluids. These methods, both of which are based on viscosity measurements, were suggested because (1) the viscosity of synovial fluid depends alinost entirely on its hyaluronic acid content; (2) the viscosity and particularly its variation with velocity gradient are sensitive to changes in the state of hyaluronic acid. Because the viscous properties vary rapidly with concentration it is necessary either to compare relationshipswhichareindependent ofconcentration or to measure and make allowance for the concentration. In Ogston & Stanier's first method, the ratios of viscosities at zero velocity gradient and at 50 sec.-1 are plotted against the viscosities at zero velocity gradient; while dilutions of a given sample of hyaluronic acid give points lying reproducibly on a single curve, different hyaluronic acids give different curves. Scott Blair, Williams, Fletcher & Markham (1954) have proposed a similar method. In their second method, the concentration of hyaluronic acid forms the basis for comparing viscosities, which may be measured under any stated conditions of flow. Sedimentation measurements were also made on a few representative fluids, in order to obtain further information on the state of their hyaluronic acid. It is concluded (i) that there are inter-species and possibly intra-species differences of the hyaluronic acid of synovial fluid; (ii) that these differences are detectable by comparing viscosities in a way not requiring measurement of concentration; (iii) that the measurement of the concentration of hyaluronic acid in human fluids presents difficulties which make comparisons of viscosity on a concentration basis of doubtful value. Having reached these conclusions, we intend, at least for the present, to discontinue this work.