NOT DESCRIBED IN PREVIOUS SECTIONS. 533 
injected subcutaneously or into the peritoneal cavity of rabbits or 
guinea-pigs, a fatal termination depends largely on the quantity in- 
jected; and although the bacillus may be obtained in cultures from 
the blood and the parenchyma of the various organs, it is not present 
inlarge numbers, and death appears to be due to toxzemia rather than 
to septicaemia. Mice are not susceptible toinfection by subcutaneous 
injections. Small quantities injected beneath the skin of guinea-pigs 
usually produce a local abscess only ; larger amounts—two to five 
cubic centimetres—frequently produce a fatal result, with symptoms 
and pathological appearances corresponding with those resulting 
from intravenous injection. These are fever, developed soon after 
the injection, diarrhoea, and symptoms of collapse appearing shortly 
before death. At the autopsy the liver and spleen appear normal, or 
nearly so; the kidneys are congested and may present scattered 
punctiform ecchymoses (Weisser). According to Escherich, the 
spleen is often somewhat enlarged. The small intestine is hyper- 
zemic, especially in its upper portion, and the peritoneal layer pre- 
sents a rosy color; the mucous membrane gives evidence of more 
or less intense catarrhal inflammation, and contains mucus, often 
slightly mixed with blood. In rabbits death occurs at a somewhat 
later date, and diarrhcea is a common symptom. In dogs the subcu- 
taneous injection of a considerable quantity of a pure culture may 
give rise to an extensive local abscess. 
In human pathology the colon bacillus plays an important réle. . 
It is concerned in the etiology of a considerable proportion of the 
cases of cystitis and of pyelonephritis, and peritonitis resulting from 
perforation. It appears to be the cause of certain affections of the 
anal region (Hartmann and Lieffring). It has been obtained in pure 
culture from abscesses in various parts of the body, from the valves 
of the heart in endocarditis, from the pleural cavity in empyema, etc. 
It has also been found in the blood, as a result of general infection 
following cystitis and pyelonephritis (Sittmann and Barnow). 
Varieties.—Booker, in his extended studies relating to the bac- 
teria present in the faeces of infants suffering from summer diarrhea, 
has isolated seven varieties “ which closely resemble Bacterium coli 
commune in morphology and growth in agar, neutral gelatin, and 
potato, but by means of other tests a distinction can be made between 
them.” 
Some of the pathogenic bacteria heretofore described are also 
closely allied to the “colon bacillus” and by some bacteriologists are 
supposed to belong to the same group—7.e., to be varieties of the 
same species rather than independent species with fixed characters. 
Whatever may be the remote relationship, the typhoid group, the hog- 
