The effect of temperature on the viscosity characteristics of erythrocytes suspended in plasma, serum, buffer and fibrinogen or dextran solutions and of the suspending phases have been compared. All the suspending phases obey the relationship
where η is the viscosity, T temperature (°K) and A and c are constants. The value of A varies with solute concentration but that of c is common to all of these solutions. The cell suspensions obey a similar relationship, but the value of c increases abruptly below about 22°C suggesting that a membrane phase transition occurs at about that temperature. The data indicate that rouleaux formation is temperature dependent whether induced by dextran, fibrinogen or serum proteins. However, they also indicate that dextran has a mode of interaction with the erythrocyte which differs from that of the proteins.
