Tissue Cultures in Typhus 



271 



Rocky Mountain spotted fever the bits of tissue were taken 

 from the tunica of the testes. With typhus the cerebral cortex 

 was used. The plasma was obtained from adult normal guinea 

 pigs by centrifuging chilled blood collected in paraffined tubes. 



Our results with spotted fever prove that the virus survives 

 and multiplies in such cultures. Evidence of survival of the 

 virus was obtained by causing the disease in guinea pigs by 

 injecting the cultures intraperitoneally. Although the spotted 

 fever reaction is very characteristic, the results were controlled 

 by histological studies or by subsequent immunity tests. 



Evidence of multiplication of the virus was obtained by 

 demonstration of the minute paired micro-organism of the dis- 

 ease (Dermacentroxenusrickettsi) in increasing numbers in first 

 generation cultures up to about the fourteenth day. The micro- 

 organisms are always intracellular, in large amoeboid phagocytic 

 cells of endothelial origin. 



The accompanying table shows the duration of survival of 

 the micro-organisms in first "generation" cultures, experiments 

 of August 17, October 10 and October 24, and the prolonga- 

 tion of this period by transplanting the cultures into fresh plas- 

 ma; experiments of October 31 and November 7. 



The examination of cultures fixed in Zenker's fluid, sectioned 

 and stained with Giemsa's stain, shows that the period of sur- 

 vival of the micro-organisms corresponds to the length of sur- 

 vival of the cells of the culture. Initial multiplication of the 

 micro-organisms takes place in situ in endothelial cells of blood 

 vessels, and continues in wandering cells of the same origin. 



In addition to the forms of the micro-organism previously 

 described, filamentous forms are occasionally found resembling 

 those of Rickettsia prowaseki as seen in infected lice. 



With typhus we have not completed experiments beyond first 

 "generation" cultures. Guinea pigs inoculated after eight, eleven 

 and fourteen days incubation of the cultures have acquired 

 typhus, as was proved by typical temperature reaction plus char- 

 acteristic lesions in the brain or immunity. 



Micro-organisms consistent with Rickettsia prowazeki have 

 been found in sections of the brain cultures within large wan- 

 dering amoeboid cells; but their demonstration is attended with 

 the same difficulties in these tissue cultures as in sections of fresh 

 tissues with lesions. The examination of sections of the cul- 

 tures shows that the surviving cells in these brain cultures take 



