396	PATHOGENIC BACTERIA.
dysentery, the bacillus not only seems to acquire an un-
usual degree of virulence, but because of the existing
denudation of mucous surfaces, etc., finds it easy to enter
the general system, with the result of secondary remote
suppurative lesions in which it is the essential factor.
When absorbed from the intestine it frequently enters
the kidney and is excreted with the urine, causing, inci-
dentally, local inflammatory areas in the kidney, and
occasionally cystitis. A case of urethritis is reported to
have been caused by it.
In infants cholera infantum may not infrequently be
caused by the colon bacillus, though probably in this
disease other bacteria play a very important role.
The bile-ducts are very often invaded by the bacillus,
which may cause inflammation, obstruction, suppuration,
or calculous formation.
The bacillus has also been met in puerperal fever,
WinckePs disease of the new-born, endocarditis, menin-
gitis, liver-abscess, bronchopneumonia, pleuritis, chronic
tonsillitis, and urethritis.
For the determination of the colon bacillus the im-
portant points are the motility, the indol reaction, the
milk-coagulation, and the active gas-production. As,
however, all of these features are shared by other bac-
teria to a greater or less degree, the only positive differ-
ential point upon which very great reliance can be placed
is the immunity-reaction of the serum of an immunized
animal, which not only protects susceptible animals from
the effects of inoculation, but produces with fresh cul-
tures of the bacillus exactly the same reaction as that
observed in connection with the blood and serum of
typhoid patients, and convalescents and immunized ani-
mals. This reaction has been considered at length in
speaking of typhoid fever.
For the few who are convinced that the colon and
typhoid bacilli are identical, the fact that the typhoid
serum is specific for the typhoid bacillus, and the colon
serum for the colon bacillus, with rare exceptions,