[Blood relapses and modifications of the pre-erythrocytic shizonts of Plasmodium yoelii using ethionine]

Injections of DL-ethionine during the preerythrocytic period of Plasmodium yoeli in Thammomys were followed by: 1. A delayed prepatent period; 2. A relapsing parasitaemia with alternatively positive and negative blood at subinoculation of clean mice; 3. A peculiar morphology of the exoerythrocytic schizonts which remain small with a scanty cytoplasm and very few large nuclei. Although the authors consider the origin of the relapses to be the rupture of delayed hepatic schizonts under the influence of ethionine, none were found after the 5th day.