SPIROCHZTA BALBIANIL AND SPIROCHETA ANODONTH. 57 
Forms like Treponema pallidum, without membranes, 
are now not included in the genus Spirochexta, and in 
Treponema the coils do not result from movement, but are 
apparently preformed. Similarly, an organism described by 
Castellani from “‘ yaws” (S. pertenuis) is not a true Spiro- 
chete. However, S. refringens (Schaudinn), a form asso- 
ciated with Treponema pallidum in syphilitic lesions, 
remains in the genus. 
Some of the well-known species of the genus beside 8. 
balbianii and 8, anodonte are: 
S. obermeieri (Cohn), from human relapsing fever. 
S. anserina (Sakharoff), from the blood of geese. 
S. gallinarum (Marchoux and Simond), from the 
blood of fowls. 
S. duttoni (Breinl and Kinghorn), from African tick 
fever in man. . 
S. refringens (Schaudinn), associated with Trepo- 
nema pallidum in syphilitic lesions. 
S. buccalis (Cohn). 
S. dentium (Koch), from the human mouth. 
S. muris (Wenyon) or 8S. laverani (Breinl and 
_ Kinghorn), from the blood of mice. 
The accounts of the structure of most of these forms are 
either incomplete or disputed, and often turn on the presence 
of a membrane and lack of flagella. There are other doubt- 
ful species, and the whole matter is discussed by Blanchard 
(13), who also gave a list of species. 
Finally, the above is only provisional, and personally I 
think it is, perhaps, preferable to state that the Spirochetes 
are annectant forms between strict Bacteria and_ strict 
Protozoa. This may savour of begging the question of the 
systematic position of the Spirochetes, but Nature does not 
set arbitrary boundaries marked off by hard and fast lines. 
In the evolution of any two distinct forms numerous transi- 
tional ones occur, and classification is only intended to mark 
the state of our knowledge for the time being, 
