432 PA THOGENIC BA CTERIA. undergoes a peculiar cycle of changes according to the stage of the disease. During the pyrexia the organisms are found in the blood in active movement, swimming both by rotation on the long axis and by undulation. As soon as the crisis comes on they are found to be with- out motion, most of them enclosed in leucocytes and seemingly dead. The recurrence of the paroxysm has suggested to many that spores are formed in the spiril- lum, but no one has been successful in proving that this is the case. Koch, Carter, and Soudakewitch have all succeeded in giving the disease to monkeys, and Munch and Moczutkowsky have gone further and have produced it in men by introducing into them blood from diseased patients. Soudakewitch finds that the removal of the spleen causes the disease to terminate fatally in monkeys.