678 DISEASES CAUSED BY FILTRABLE VIRUS 



that occasionally inoculation with filtered blood renders monkeys re- 

 fractory to later inoculation, it is generally believed at present that the 

 disease is caused by some agent too large to pass through the Berke- 

 feld or Chamberland filters. 



Work on the etiology of typhus has been very extensive and many 

 microorganisms have been described. 



Ricketts and Wilder saw short bacilli in smear preparations, but were not 

 able to cultivate them. Rabinovitch 1 described a Gram-positive diplo-bacillus, 

 cultivated from cases of an epidemic in Kieff, and with antigens prepared from 

 this organism, he obtained complement-fixation and agglutination. Fvirth 

 studied an epidemic in China and obtained short, plump rods which grew aero- 

 bically in short chains. P. Th. Muller saw a diplo-bacillus upon which he did 

 not lay much stress etiologically, and Prowezek described inclusions in euco- 

 cytes which he regarded as protozoa. It is hardly worth while at the present 

 time to describe in detail the many different findings that have been reported, 

 since hi few of them is there sufficient evidence to enable us to come to con- 

 clusions. 



In 1914 Plotz 2 described a short Gram-positive bacillus which he 

 obtained by anaerobic cultivation, with considerable regularity, from 

 cases of Brill's disease at the Mt. Sinai Hospital, New York, and which 

 since then has been made the subject of considerable study by Plotz, 

 Olitsky, and Baehr. 3 They have obtained the bacillus again and again, 

 have succeeded in obtaining positive agglutinations and complement- 

 fixation in the blood of endemic typhus cases after the crisis and have 

 obtained a similar bacillus from a number of European typhus cases 

 which have come into quarantine. 



The method of cultivation by which this bacillus is grown is 

 relatively simple, consisting of taking blood directly from a vein into 

 high tubes containing glucose agar and unheated and unfiltered ascitic 

 fluid of a specific gravity not less than 10.15. 



The American Red Cross Commission which went to Serbia during the last 

 typhus epidemic and of which the writer was a member attempted to work 

 along the lines laid down by Plotz but found it extremely difficult to do sys- 

 tematic work and obtain reliable materials under the conditions then existing. 

 The undersigned obtained an organism very similar to the Plotz bacillus by 

 Plotz's method in two cases. In the first of these the organism could not be 

 carried further than the second generation, and in the second it did not reach 

 America alive. Hopkins obtained a similar organism later toward the end of 



1 Rabinovitch, Centralbk. Bakt. Orig., 1909, lii, Arch. f. Hyg., 1909. 



2 Plotz, Jour, of A. M. A., Ixii, 20, p. 14. 



3 Plotz, Olitsky and Baehr, Jour, of Inf. Dis., xvii, 1915, p. 1. 



