524 TREPONEMATA AND SPI ROCHET A 



of Treponema recurrentis in defibrinated rat's blood and succeeded 

 in keeping these organisms alive on blood agar for forty days, at the 

 end of which time they were still infective for rats. No actual mul- 

 tiplication, however, was observed in this medium. Noguchi 1 has 

 grown the organisms in pure culture, using the method described 

 previously (see Treponema pallidum). The organisms develop with 

 considerable rapidity, a distinct clouding of the medium being 

 observed after twenty-four to forty-eight hours' incubation at 37 C. 

 The maximum growth is reached at the end of a week. 



Pathogenesis. Animal. Pure cultures retain their original virulence 

 for rats and mice for several transfers in the agar ascitic fluid tissue 

 medium described by Noguchi. The lesions produced in experimental 

 animals are essentially the same as those observed in man. The disease 

 can be transmitted by inoculation from man to monkeys, from monkey 

 to monkey, and from monkey to mice and rats, which are all suscep- 

 tible. Rabbits and guinea-pigs appear to be refractory. The disease 

 produced by inoculation of the organisms in monkeys and mice 

 exhibits the characteristic relapses, and it may be fatal. 



Human. There are no characteristic lesions observed in relapsing 

 fever other than a hyperplastic enlargement of the spleen. There 

 may be a catarrhal inflammation of the stomach, bile ducts and liver, 

 which is usually enlarged. All of the organs exhibit parenchymatous 

 degeneration postmortem. 



Bacteriological Diagnosis. The organisms are found in the blood 

 stream only during the paroxysms. During the period of apyrexia 

 they disappear from the blood stream, but are found in the spleen 

 in large numbers, where they are engulfed by leukocytes. 



Immunity. According to Novy, 2 blood drawn from a patient at 

 the beginning of the fever acts as a good culture medium for the 

 organisms; that drawn at the end of a paroxysm or after recovery from 

 the disease appears to possess germicidal properties for the organisms. 

 It is supposed that the organisms are taken up by phagocytes during 

 the afebrile periods, and that they are either weakened or killed at 

 this time. Active immunity follows recovery from the infection. It 

 has been claimed that the blood serum of immunized animals (which 

 exhibit immunity after repeated injections of the organism) or of 

 animals which have recovered from an attack will induce passive 

 immunity and temporarily prevent infection when it is introduced 

 into susceptible animals prior to inoculation of the organisms. 



1 Loc. cit., p. 208. 2 Jour. Inf. Dis., 1906, iii, 291. 



