308 PATHOGENIC BACTERIA. 



not by Gram's method. It seems to be a strict parasite, 

 and has never been cultivated artificially. 



Of the pathogenesis of the organism there can be no 

 doubt, as it is invariably present in relapsing fever and 

 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. 



