In spite of the many studies on the rate of erythrocyte sedimentation, the theory behind the variations in the rate remains clouded. The fundamental basis for this phenomenon, as in the Wassermann reaction, may even remain hidden long after the practical applications have become well understood. It seems to be clear that the normal variation in the rate of red blood cell sedimentation, when tested by any one of several methods, is not great. With the exception of certain physiologic states, such as menstruation and pregnancy, the limits of normal are fairly well defined. The disturbance in the stability of the blood that occurs in certain diseases does not seem to be specific. It does appear, however, according to some observers, to parallel with considerable accuracy the degree of activity of the disease.
The performance of this relatively new laboratory procedure is simple, whether by the methods of Westergren or