942 DISEASES CAUSED BY FILTRABLE VIRUS 



Arnheim obtained his organism from six eases, on ascitic agar plates, on 

 which on the first cultures there appeared a growth hardly visible to the 

 naked eye and which in transplants continued to grow very delicately. He 

 states his organism is not unlike that of Petruschky and he obtained it out 

 of the blood, the sputum and the urine of typhus cases. 



A serious objection to the acceptance of the Plotz bacillus is that, 

 despite the fact that a great many workers have been studying this 

 disease during the last few years, the microorganisms which have 

 been described have not been similar one with the other, and the 

 fact that Plotz organism seems to lose its virulence immediately upon 

 artificial cultivation. Also according to Anderson, active immuniza- 

 tion with the Plotz bacillus does not render guinea-pigs refractory to 

 virus inoculation. 



Careful experiments at the Washington Hygienic Laboratory also have 

 shown that the inoculation of large amounts of living Plotz organisms will 

 neither injure nor immunize guinea-pigs or monkeys, whereas a single injec- 

 tion of typhus blood, after causing the typical curve, leaves these animals 

 refractory to further inoculation. 



In the course of the war a great deal of further etiological research was 

 done on typhus incidental to which, naturally, renewed search for bacterial 

 causative agents was made. Gotschlich 18 in reviewing this work finds that 

 only two other investigators, Paneth and Popoff, found organisms similar 

 to the Plotz bacillus. Gotschlich believes, as we do, that the etiological 

 relationship of the Plotz bacillus has by no means been proven and is unlikely. 

 The indirect evidence adduced by Plotz and his associates with agglutination 

 reactions, etc., has lost a great deal of its value in view of the more recent 

 work done on the Weil-Felix reaction in which a species of proteus is 

 agglutinated with considerable regularity by typhus blood. 



It is quite impossible to review completely the enormous bac- 

 teriological literature that has grown up about claims of causative 

 relationship for many isolated organisms. In none of them could 

 absolute proof be adduced and such claims seem to become less 

 and less important as we follow the more recent developments 

 concerning the so-called Rickettsia bodies. 



In 1909 Ricketts 19 saw small bacillus-like bodies in the blood 

 of guinea-pigs he had infected with Rocky Mountain Spotted Fever, 



18 Gotschlich, Erg. d. Hyg. Bakt., Berlin, 245, 1917. 

 "Ricketts, Medical Record, 76, 1909, 842. 



