stain.

_Variations from Typical Pus._--Pus from old-standing sinuses is often
watery in consistence (ichorous), with few cells. Where the granulations
are vascular and bleed easily, it becomes sanious from admixture with
red corpuscles; while, if a blood-clot be broken down and the debris
mixed with the pus, it contains granules of blood pigment and is said to
be "grumous." The _odour_ of pus varies with the different bacteria
producing it. Pus due to ordinary pyogenic cocci has a mawkish odour;
when putrefactive organisms are present it has a putrid odour; when it
forms in the vicinity of the intestinal canal it usually contains the
bacillus coli communis and has a fæcal odour.

The _colour_ of pus also varies: when due to one or other of the
varieties of the bacillus pyocyaneus, it is usually of a blue or green
colour; when mixed with bile derivatives or altered blood pigment, it
may be of a bright orange colour. In wounds inflicted with rough iron
implements from which rust is deposited, the pus often presents the same
colour.

The pus may form and collect within a circumscribed area, constituting a
localised _abscess_; or it may infiltrate the tissues over a wide
area--_diffuse suppuration_.


ACUTE CIRCUMSCRIBED ABSCESS

Any tissue of the body may be the seat of an acute abscess, and there
are many routes by which the bacteria may gain access to the affected
area. For example: an abscess in the integument or subcutaneous