SUMMARY 127 



long periods (four months). This is in great contrast to the 

 behavior of the viruses of typhus and of Rocky Mountain 

 spotted fever. 



Rickettsia prowazeki: Is strikingly pleomorphic, multiplies 

 exclusively within cells in the louse and is very susceptible to 

 drying and heat. Da Rocha-Lima has produced some evidence 

 that in the louse it is transmitted hereditarily. 



Rickettsia rocha-lima: Weigl in Warsaw in 1920 showed us 

 preparations of lice containing intracellular pleomorphic 

 rickettsi indistinguishable by us from Rickettsia prowazeki 

 (Fig. 2, plate I). According to Weigl this is a non-pathogenic 

 rickettsia infecting man, and was acquired by lice fed upon 

 himself and upon members of Denekine's army. We are not 

 convinced that Weigl was dealing with a rickettsia other 

 than Rickettsia prowazeki. 



Rickettsia lectularius: Arkwright, Atkins, and Bacot, 1921, 

 is an extremely interesting micro-organism, morphologically 

 very similar to Rickettsia prowazeki in pleomorphism and stain- 

 ing. It is non-pathogenic and is apparently widely distributed 

 in bedbugs in England and Europe. (Fig. 19, plate IV, illus- 

 trates a smear, made by Mr. Bacot, of a bedbug caught in 

 Warsaw.) It multiplies exclusively intracellularly in various 

 organs of the bedbug and is transmitted hereditarily. Ark- 

 wright, Atkins, and Bacot describe a morphological cycle or 

 sequence of forms, similar to that of Rickettsia prowazeki and 

 Dermacentroxenus rickettsi. 



The unnamed rickettsia from Culex pipiens discovered by 

 Noller and referred to by Sikora, 1920, occurs extracellularly 

 in the mosquito. No further data are furnished. 



Rickettsia ctenocephali: Sikora (1918), is a non-pathogenic 

 micro-organism exhibiting large and small forms, but it is not 

 as pleomorphic as Rickettsia prowazeki and Rickettsia lectula- 

 rius. It occurs in the coelom of the cat flea and is transmitted 

 hereditarily. 



The unnamed rickettsia from the mouse flea was briefly 

 mentioned by Sikora in 1918. It occurs intracellularly in the 

 Malpighian tubules. 



