1. The erythrocyte factor in the blood sedimentation phenomenon is not influenced by changes in size or shape of the erythrocytes unless the surface is altered by a hemolytic agent.
2. The erythrocyte factor varies considerably in health and disease. It is depleted when blood is stored under refrigeration.
3. Egg lecithin emulsions and particles of cinnabar covered with lecithin are flocculated by gelatin solutions. The phenomenon is similar to the formation of rouleaux in gelatin solutions.
4. An attempt to explain rouleau formation as a flocculation reaction between plasma proteins and the lecitho-protein surface of the erythrocyte is made.