inflammation of serous and synovial membranes, also with a form of
pneumonia which is prone to follow on severe operations in the mouth and
throat. Streptococci are also concerned in the production of spreading
gangrene and pyæmia.

Division takes place in one axis, so that chains of varying length are
formed (Fig. 3). It is less easily cultivated by artificial media than
the staphylococcus; it forms a whitish growth.

[Illustration: FIG. 4.--Bacillus coli communis in Urine, from a case of
Cystitis. × 1000 diam. Leishman's stain.]

_Bacillus Coli Communis._--This organism, which is a normal inhabitant
of the intestinal tract, shows a great tendency to invade any organ or
tissue whose vitality is lowered. It is causatively associated with such
conditions as peritonitis and peritoneal suppuration resulting from
strangulated hernia, appendicitis, or perforation in any part of the
alimentary canal. In cystitis, pyelitis, abscess of the kidney,
suppuration in the bile-ducts or liver, and in many other abdominal
conditions, it plays a most important part. The discharge from wounds
infected by this organism has usually a fœtid, or even a fæcal odour,
and often contains gases resulting from putrefaction.

It is a small rod-shaped organism with short flagellæ, which render it
motile (Fig. 4). It closely resembles the typhoid bacillus, but is
distinguished from it by its behaviour in artificial culture media.

[Illustration: FIG. 5.--Fraenkel's Pneumococci in Pus from Empyema
following Pneumonia. × 100 diam. Stained with Muir's capsule stain.]