[Erythrocyte form and deformability for normal blood and some hereditary hemolytic anemias (author's transl)].

1. A brief review of recent results on the structure of erythrocyte membranes and the experimental deformation of red blood cells. 2. A discussion of factors playing a role in the deformability: a) Influence of shape, consisting of the cell surface to volume ration. b) Internal factors, depending mainly on the viscosity of the hemoglobin).c) Degree of flexibility of the membrane. 3. A brief summary of techniques to measure the deformability with emphasis on the method of viscodiffractometry (ektacytometer). 4. Results given by examination in the ektacytometer of hereditary spherocytosis and sickle cell anemia.