Abstract
A technique is described for automatically measuring the rate at which erythrocytes pack together during centrifugation, by photographically recording the transmission of light through a micro-capillary centrifuge tube. Differences between curves obtained in this way are shown to indicate a change of flexibility of the erythrocytes; for instance, after treatment with formaldehyde the rate is much slower than with normal cells. A comparison with a procedure involving stopping and starting the centrifuge indicates that no re-expansion or change occurs on slowing the speed of rotation.