[Illustration: FIG. 2.--Staphylococcus aureus in Pus from case of
Osteomyelitis. x 1000 diam. Gram's stain.]
_Staphylococcus Aureus._--This is the commonest organism found in
localised inflammatory and suppurative conditions. It varies greatly in
its virulence, and is found in such widely different conditions as skin
pustules, boils, carbuncles, and some acute inflammations of bone. As
seen by the microscope it occurs in grape-like clusters, fission of the
individual cells taking place irregularly (Fig. 2). When grown in
artificial media, the colonies assume an orange-yellow colour--hence the
name _aureus_. It is of high vitality and resists more prolonged
exposure to high temperatures than most non-sporing bacteria. It is
capable of lying latent in the tissues for long periods, for example, in
the marrow of long bones, and of again becoming active and causing a
fresh outbreak of suppuration. This organism is widely distributed: it
is found on the skin, in the mouth, and in other situations in the body,
and as it is present in the dust of the air and on all objects upon
which dust has settled, it is a continual source of infection unless
means are taken to exclude it from wounds.
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