cer. Certain forms of
_bed-sore_ are also due to prolonged pressure.

Pressure sores are also known to have been produced artificially by
malingerers and hysterical subjects.

[Illustration: FIG. 14.--Leg Ulcers associated with Varicose Veins and
Pigmentation of the Skin.]

_Ulcers due to Imperfect Circulation._--Imperfect circulation is an
important causative factor in ulceration, especially when it is the
_venous return_ that is defective. This is best illustrated in the
so-called _leg ulcer_, which occurs most frequently on the front and
medial aspect of the lower third of the leg. At this point the
anastomosis between the superficial and deep veins of the leg is less
free than elsewhere, so that the extra stress thrown upon the surface
veins interferes with the nutrition of the skin (Hilton). The importance
of imperfect venous return in the causation of such ulcers is evidenced
by the fact that as soon as the condition of the circulation is improved
by confining the patient to bed and elevating the limb, the ulcer begins
to heal, even although all methods of local treatment have hitherto
proved ineffectual. In a considerable number of cases, but by no means
in all, this form of ulcer is associated with the presence of varicose
veins, and in such cases it is spoken of as the _varicose ulcer_ (Fig. 14).
The presence of varicose veins is frequently associated with a
diffuse brownish or bluish pigmentation of the skin of the lower third
of the leg, or with an obstinate form of dermatitis (_varicose eczema_),
and the scratching or rubbing of the part is liable to cause a breach of
the surface and permit of infection which leads to ulceration. Varicose
ulcers may also originate from the bursting of a small peri-phlebitic
abscess.

Varicose veins in immediate relation to the base of a large chronic
ulcer usually become thrombosed, and in time are reduced to fibrous
cords, and therefore in such cases haemorrhage is not a common
complication. In smaller and more superficial ulcers, however, the
destructive process is liable to implicate the wall of the vessel before
the occurrence of thrombosis, and to lead to profuse and it may be
dangerous bleeding.

These ulcers are at first small and superficial, but from want of care,
from continued standing or walking, or from injudicious treatment, they
gradually become larger and deeper. They are not infrequently multiple,
and this, together with their depth, may lead to their