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Chapter XXXI 
Spirochaetes 
The Spirilla are distinguished from the spiro¬ 
chaetes : (i) bp their inflexible body, (2) by the 
possession of a tuft of terminal flagella, (3) by their 
having a firm cuticular cell wall, as other bacteria, 
capable of resisting the action of ten per cent, potash, 
whereas spirochaetes are completely dissolved. What 
spirochaetes are, is a matter of great dispute. By some 
authors they are considered to be flagellates, by others 
bacteria. 
Spirochaeta .—May provisionally be defined as 
follows :—Body not spiral (?) but shewing regular 
snake-like undulations in the same plane, consisting of 
sheath or periplast (? undulating membrane) and 
endoplasm. Division transverse (? also longitudinal), 
the two separating portions being often joined by a 
fine thread, the length of the two young individuals 
being equal to that of the original spirochaete. A 
terminal appendage (flagellum) can be shewn by special 
methods, but it may simply be a portion of the above 
thread or elongated sheath. Bacterium-like flagella 
exceedingly doubtful. They may be the frayed-out 
ectoplasmic sheath. 
Encysted Forms .—Just before the crisis in the case 
of Sp. duttoni , Breinl described the formation of cysts in 
the spleen. The spirochaete becomes rolled up into 
tangles and is generally eaten up by phagocytes, but 
some few become encysted, the contents of the cyst 
breaking up into small granules. It is possibly from 
these granules that the new generation of spirochaetes 
develops. 
