546 A MANUAL OF BACTERIOLOGY 



day of the disease. It is also found in infected lice, but 

 could not be cultivated. A similar micro-organism was 

 also observed in Mexican typhus blood by Gavino and 

 Girard, and by Campbell, and the latter also finds that 

 the blood is not infective if passed through a Chamberland 

 F filter. 



Ricketts and Wilder also discuss the relationship between 

 typhus fever and Rocky Mountain spotted fever. 1 Some 

 years ago Wilson and Chowning made observations on a 

 typhus-like fever occurring in limited tracts of country 

 near the Rocky Mountains and ascribed it to a Piroplasma. 

 Subsequent research, however, failed to confirm this, 

 though the disease appears to be conveyed by a tick, and 

 not by fleas, lice, etc. There are clinical differences 

 between typhus and Rocky Mountain spotted fever ; more- 

 over, the guinea-pig is susceptible to the spotted fever 

 but not to typhus, and a monkey immunised to typhus is 

 susceptible to spotted fever. Ricketts believes that the 

 spotted fever is due to a bacillus which can be found 

 in the ovary of the tick and is agglutinated by the serum 

 in dilutions of 1-500. 



Cathoire has made observations on complement fixation 

 in typhus. Using as an antigen an alcoholic extract of 

 typhus spleen, marked complement fixation was obtained 

 with the serum of typhus cases. 



Yellow Fever 



As far back as 1889 Sternberg described a bacillus 

 " Bacillus X " in yellow fever, a facultative anaerobic 

 organism, very pathogenic to rabbits. In 1897 Sanarelli 2 

 described his Bacillus ictero'ides, which later investigation 



1 The name is an unfortunate one, for this disease is quite distinct 

 from " spotted fever " epidemic cere bro -spinal meningitis. 



2 Ann. de VInst. Pasteur, xi, 1897, pp. 443, 673, and 753. 



