334 CLINICAL BACTERIOLOGY. 



human body. They have been found once in the urine in 

 a case of relapsing nephritis. The relapsing spirilla are, 

 therefore, most rigid blood-parasites. 



Transmission of Relapsing Fever. Relapsing fever 

 has been repeatedly transmitted to healthy human beings, 

 and with complete success to apes, by means of blood con- 

 taining spirilla (Koch, Carter, and others). The spirilla 

 can thus with certainty be considered as the exciting agents 

 of relapsing fever. How they induce the disease, and 

 whether the fever is the result of a poison generated by 

 them, can not yet be decided positively. Equally little is 

 known with regard to the manner in which the disease is 

 transmitted naturally. . The disease is contagious ; as, how- 

 ever, the spirilla soon lose their vitality outside of the body 

 in water, on articles of food, in the air the ordinary modes 

 of infection, by way of the respiratory or the digestive tract, 

 are scarcely to be considered. The disease can be conveyed 

 only with the blood, as the spirilla apparently do not leave 

 this fluid. Klebs refers to the possibility of conveyance 

 through blood-sucking cutaneous parasites, but this has not 

 been established with certainty. Intrauterine transmission 

 of the spirilla to the fetus has been observed. 



The mode of recovery from relapsing fever, which, as 

 is known, thus terminates in the majority of cases, is essen- 

 tially not yet understood. According to Heydenreich, the 

 bacilli die as a result of the high temperature of the patient 

 in the febrile attack. His observations, however, as has been 

 pointed out, do not furnish adequate evidence in support of 

 this view. According to Metschnikoff, the spirilla collect 

 in the spleen during the precritical elevation of temperature, 

 and are there destroyed by phagocytosis. Baumgarten 

 does not consider this a healing process, but believes that 

 the spirilla are deposited in the spleen, and also in the liver 

 and the bone-marrow, where they undergo destruction, in 

 part through inclosure in leukocytes, and in part indepen- 

 dently of this process ; but this takes place only because 

 they have ceased proliferating, because their vital activity 

 has been impaired, and they are nearly or already dead. 

 The cause of this attenuation Baumgarten believes to re- 

 side in spontaneous exhaustion of the proliferating power 

 of the infecting microbes, which are endowed with only a 

 short duration of life in consequence of immanent vital 

 laws. The successive febrile cycles are attributed by 



