Abstract
A simple method of determining osmotic thrombocyte resistance by means of photo-electric measurement is described, and normal values are established from the graphs obtained. Osmotic platelet changes being at NaCl concentrations of 0.45-0.35% and continue in decreasing concentrations to distilled water. A thrombocyte count of 300,000-500,000 per cu.mm. is the most suitable for this investigation, though smaller numbers still give reliable results.