Blood from healthy animals and humans contains nondiscocytic erythrocytes.

Blood samples (three drops) from healthy animals and humans were fixed in a 2.5% solution of glutaraldehyde in 0.1 M cacodylate buffer at pH 7.4 within seconds of being drawn. Dehydrated and gold-coated preparations were photographed at x 600 in a scanning electron microscope, then printed at x 1200. Erythrocytes were classified according to their shape and surface features into six classes, namely, normal red cells, flat cells, cells with surface changes, early cup forms, late cup forms, cells with altered margins. The size of each shape-determined class was expressed as a percentage of the total number of cells counted. Data relating to 23 healthy females and to a mouse, rat, rabbit and horse are reported. Although the presence of nondiscocytic erythrocytes in peripheral human blood has been described, the presence of similar cells in animal blood has not been reported previously.