being mistaken
for ulcers due to syphilis. The base of the ulcer is covered with
imperfectly formed, soft, oedematous granulations, which give off a thin
sero-purulent discharge. The edges are slightly inflamed, and show no
evidence of healing. The parts around are usually pigmented and slightly
oedematous, and as a rule there is little pain. This variety of ulcer is
particularly prone to pass into the condition known as callous.

In _anaemic_ patients, especially young girls, ulcers are occasionally
met with which have many of the clinical characters of those associated
with imperfect venous return. They are slow to heal, and tend to pass
into the condition known as weak.

_Ulcers due to Interference with Nerve-Supply._--Any interference with
the nerve-supply of the superficial tissues predisposes to ulceration.
For example, _trophic_ ulcers are liable to occur in injuries or
diseases of the spinal cord, in cerebral paralysis, in limbs weakened by
poliomyelitis, in ascending or peripheral neuritis, or after injuries of
nerve-trunks.

The _acute bed-sore_ is a rapidly progressing form of ulceration, often
amounting to gangrene, of portions of skin exposed to pressure when
their trophic nerve-supply has been interfered with.

[Illustration: FIG. 15.--Perforating Ulcers of Sole of Foot.

(From Photograph lent by Sir Montagu Cotterill.)]

The _perforating ulcer of the foot_ is a peculiar type of sore which
occurs in association with the different forms of peripheral neuritis,
and with various lesions of the brain and spinal cord, such as general
paralysis, locomotor ataxia, or syringo-myelia (Fig. 15). It also occurs
in patients suffering from glycosuria, and is usually associated with
arterio-sclerosis--local or general. Perforating ulcer is met with most
frequently under the head of the metatarsal bone of the great toe. A
callosity forms and suppuration occurs under it, the pus escaping
through a small hole in the centre. The process slowly and gradually
spreads deeper and deeper, till eventually the bone or joint is reached,
and becomes implicated in the destructive process--hence the term
"perforating ulcer." The flexor tendons are sometimes destroyed, the toe
being dorsiflexed by the unopposed extensors. The depth of the track
being so disproportionate to its superficial area, the condition closely
simulates a tuberculous sinus, for which it is liable to be mistaken.
The raw surface is absolutely insensitive, so