induration of the surrounding skin and cellular tissues (Fig. 18). The
induration results from coagulation and partial organisation of the
inflammatory effusion, and prevents the necessary contraction of the
sore. The base of a callous ulcer lies at some distance below the level
of the swollen, thickened, and white edges, and presents a glazed
appearance, such granulations as are present being unhealthy and
irregular. The discharge is usually watery, and cakes in the dressing.
When from neglect and want of cleanliness the ulcer becomes inflamed,
there is considerable pain, and the discharge is purulent and often
offensive.

The prolonged hyperaemia of the tissues in relation to a callous ulcer of
the leg often leads to changes in the underlying bones. The periosteum
is abnormally thick and vascular, the superficial layers of the bone
become injected and porous, and the bones, as a whole, are thickened. In
the macerated bone "the surface is covered with irregular,
stalactite-like processes or foliaceous masses, which, to a certain
extent, follow the line of attachment of the interosseous membrane and
of the intermuscular septa" (Cathcart) (Fig. 19). When the whole
thickness of the soft tissues is destroyed by the ulcerative process,
the area of bone that comes to form the base of the ulcer projects as a
flat, porous node, which in its turn may be eroded. These changes as
seen in the macerated specimen are often mistaken for disease
originating in the bone.

[Illustration: FIG. 19.--Tibia and Fibula, showing changes due to
chronic ulcer of leg.]

The _irritable condition_ is met with in ulcers which occur, as a rule,
just above the external malleolus in women of neurotic temperament. They
are small in size and have prominent granulations, and by the aid of a
probe points of excessive tenderness may be discovered. These, Hilton
believed, correspond to exposed nerve filaments.

_Ulcers which are spreading_ may be met with in one of several
conditions.

_The Inflamed Condition._--Any ulcer may become acutely inflamed from
the access of fresh organisms, aided by mechanical irritation from
trauma, ill-fitting splints or bandages, or want of rest, or from
chemical irritants, such as strong antiseptics. The best clinical
example of an inflamed ulcer is the venereal soft sore. The base of the
ulcer becomes red and angry-looking, the granulations disappear, and a
copious discharge of thin yellow pus, mixed with blood, escap