patients who suffer from some nerve lesion--such as anterior
poliomyelitis, or injury of the spinal cord or nerve-trunks.
Splint-pressure sores are usually situated over bony prominences, such
as the malleoli, the condyles of the femur or humerus, the head of the
fibula, the dorsum of the foot, or the base of the fifth metatarsal
bone. On removing the splint, the skin of the part pressed upon is found
to be of a red or pink colour, with a pale grey patch in the centre,
which eventually sloughs and leaves an ulcer. 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