Procedure: incision and drainage of a superficial abscess.

Pyogenic bacteria such as the Staphylococcus Aureus characteristically produce a circumscribed area of tissue necrosis leading to abscess formation. An abscess consists of (i) a central cavity containing pus, which is essentially liquefied necrotic tissue along with dead poiymorphs and bacteria (many of the latter are alive) and (ii) a surrounding wall, the inner layer of which is again necrotic tissue (not yet liquefied) called slough the outer layer is acutely inflamed tissue profusely infiltrated with polymorphs the pyogenic membrane (Fig).