The _staphylococcus albus_ is much less common than the aureus, but has
the same properties and characters, save that its growth on artificial
media assumes a white colour. It is the common cause of stitch
abscesses, the skin being its normal habitat.
[Illustration: FIG. 3.--Streptococci in Pus from an acute abscess in
subcutaneous tissue. x 1000 diam. Gram's stain.]
_Streptococcus Pyogenes._--This organism also varies greatly in its
virulence; in some instances--for example in erysipelas--it causes a
sharp attack of acute spreading inflammation, which soon subsides
without showing any tendency to end in suppuration; under other
conditions it gives rise to a generalised infection which rapidly proves
fatal. The streptococcus has less capacity of liquefying the tissues
than the staphylococcus, so that pus formation takes place more slowly.
At the same time its products are very potent in destroying the tissues
in their vicinity, and so interfering with the exudation of leucocytes
which would otherwise exercise their protective influence. Streptococci
invade the lymph spaces, and are associated with acute spreading
conditions such as phlegmonous or erysipelatous inflammations and
suppurations, lymphangitis and suppuration in lymph glands, and
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 pyaemia.
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