Electron Microscope Study of Anaplasmosis in Bovine Red Blood Cells

1. Erythrocyte membranes from calves infected with Anaplasma marginaliswere studied under the electron microscope. The classical single marginal body of the parasite appears to be constituted of a central undivided mass and peripheral elementary bodies of high electron density, 170 to 220 mμ in diameter. In some cases the whole mass of the parasite is divided into these small submicroscopic bodies. In other erythrocytes the elementary bodies are dispersed and have a tendency to grow up. Distribution curves on measurements of 119 elementary bodies are presented. 2. The presence of the submicroscopic forms of the parasite is discussed in the light of the clinical and hematological evolution of the disease, the multiplication and the probable life-cycle of the parasite within the blood stream.