The sedimentation rate of the red blood cells is now universally considered a valuable guide for determining the presence of infection in the body. Many have found it a useful indicator of activity in cases of tuberculosis. Its value in cases of acute rheumatic fever has been repeatedly demonstrated1 and it has become one of the physician's most reliable adjuncts in determining the probable cessation of activity and the duration of the period of rest for patients with this illness.One of the disadvantages of this test, however, has been the need for withdrawing blood from the veins. The objections to this procedure are obvious in pediatric work. Children dread the pain. In obese patients and in infants it is often difficult to find a vein. Further, it is desirable to spare these vessels for more important therapeutic procedures. Since the value of the sedimentation test usually depends on repeating reading at frequent intervals, it has become desirable not only to simplify the technical steps involved in the actual test but to develop a method requiring minimal amounts of blood, which could be with¬ drawn from the tip of a finger as for the ordinary blood count. The further advantage of such a method would be to make the test available in routine office and home practice. A number of instruments had already been devised when I began my search for a suitable micrometrie apparatus ; each type required some modifications of an existing macromethod, of which there were many. Landau 2 at first used capillary tubes with a bulb at one end, similar to the chamber in the blood cell pipets. He soon found that these tubes were unnecessarily long and that he could further simplify his method by reducing the length of his tubes to 12 cm. By the use of a special device he was able to draw a solution of citrate and blood directly into the capillary tube used for sedimentation. This would seem to be the ideal arrangement, but it required careful sealing of the From the Abraham Jacobi Division for