CLASSIFICATION OF THE BACTERIA. 93 
V. serpens, Miiller. 
Filament one half less in diameter than the pre- 
ceding, rigid, annulate, having two or three regular 
undulations, at least two in the shortest; height of 
one turn of the undulations 8 to 12 w, diameter 1 to 
3 yw, total length 11 to 25 yp, thickness 0.7 ~; move- 
ments analogous to those of B. subtilis ; having a cil- 
ium (Warm.). 
In numerous swarms in infusions, river water, 
etc. 
g. Spirochete, Ehrb. 
S. plicatilis, Ehrb. 
Filament not extensible, twisted in a long helix, 
flexible, the turns of the spiral near together ; suscep- 
tible of twisting upon its axis and of an undulatory 
movement; total length 180 to 200 yp. 
Rare species; in infusions, stagnant water, 
sea-water, etc. 
S. Obermeieri, Cohn. 
Does not differ from the preceding, either in size, 
conformation, or in its movements, but by its habitat 
and physiological peculiarities. 
In the blood of persons attacked by recurrent 
fever (Obermeier, 1872, Weigert, Bisch-Hirsch- 
feld, etc.) during the period of access, never 
during the remission. 
S. gigantea, Warming. Found upon the coasts of Den- 
mark; thickness of body, 3 p», height of spiral 25 p», diam- 
eter 7 to 9 p. 
