TYPHUS FEVER, TRENCH FEVER, ETC, 



959 



According to experiments of Rickctts and Wilder, da Rocha- 

 Lima, Sergent and his co-workers, some of the Rickettsia can pass 

 into the egg of the louse and thus be inherited from one generation 

 to the other. 



Most of them, unlike bacteria and more resembling protozoa, 

 appear to enter the cells of the host as intracellular parasites. 



The sub-classification of the Rickettsia has been tentatively 

 attempted by Wolbach by whose courtesy we are enabled to insert the 

 following table : 



Insects 



Arachnida 

 Acarina 



Mallophaga 

 Corrodentia 



Hemiptera 



Diptera 



Siphonaptera 



Wulhaoh's Tentative Classification 



Melophagus ovinuft (sheep "louse" or "tick") 



Rickettsia melophagi Noller 



Psocus Sp.? (dust louse) 

 Unnamed rickettsia . . . 



1917 



Sikora 1918 



Pediculus humanus (human louse) 



Rickettsia prowazeki Hegler and yon Prowazek. . 



da Rocha-Lima 



Rickettsia (rocha-lima?) Weigl, oral statement 



Rickettsia pediculi Munk and da Rocha-Lima. 



Rickettsia quintana Munk and da Rocha-Lima. 



Rickettsia wolhynica Toepfer 



Cimex (Acanthia) lectularius (bed bug) 



Rickettsia lectularius . . . . Bacot . . 



1914 

 1916 

 1920 

 1917 

 1917 

 1916 



1921 



Culex pipiens (Mosquito, Europe) 



Unnamed rickettsia Noller, quoted by Sikora. . . 1920 



( Ctenocephalus felis (cat flea) 



Rickettsia ctenocephali Sikora 1918 



Cfenopsylla musculi (mouse flea) 



Unnamed rickettsia ... . . Sikora . . 



1918 



Dermacentor venustus (wood tick, U. S.) 

 Dermacentroxenus rickettsi . . 



.Ricketts... . 1909 



Leplus (Tromibidium) akamushi (harvest mite, Japan) 

 Unverified quotation by Sikora 



Dermanyssu* Sv.f (bird mite, Europe) 



Unnamed, Noller; quoted by Sikora 



1920 



1920 



In proposing this classification, however, it should be said in 

 justice to Wolbach that he introduces it by stating definitely that 

 a reliable classification of the Rickettsia is impossible at the present 

 time, and that he believes that there have already been included 

 under this heading a number of unrelated forms. He states that 

 the Rickettsia of the sheep louse has little to distinguish it from 

 bacteria and that the Rickettsia seen in connection with typhus 

 fever has peculiarities which separate it from others. The Rickettsia 

 studied by him in connection with Rocky Mountain Spotted Fever 

 resembles somewhat the Rickettsia-prowazeki seen in typhus, and 

 both of them are quite unlike the "morphologically simple " one 

 observed in connection with trench fever. Wolbach summarizes his 

 reasons for constructing a table of classification by saying that he 

 believes it warranted since "they are forms of microorganisms 



