Scanning electron micrographs of Heinz body laden erythrocytes. From: Jain & Keeton (1975) Am J Vet Res 36; 1691-95. Red cell inclusions can arise from a variety of sources. Some, such as the large Heinz bodies shown in the figure, can barely escape detection while others, such as small siderotic inclusions, often are not even noticed. Correct identification of these abnormalities is important since it can provide insights into metabolic, physiologic, and pathologic conditions affecting the red cells.