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140 DENTAL MEDICINE.
ulcer is characterized by abrupt edges showing no tendency to
cicatrize, and extreme tenderness or sensitiveness. The fun-
gous ulcer is characterized by an exuberant growth of granula-
tions. The hemorrhagic ulcer is characterized by a tendency to
bleeding upon the least provocation, and is common to scurvy.
Torpid ulcers are those which manifest no disposition of activity
in any direction. Callous ulcers are characterized by a dirty,
granulating surface covered with thin, muco-purulent pus, and
prominent edges. Corroding ulcers are destructive, progressively,
of soft tissues, beginning as a cutaneous disease, which becomes
a boil and afterward an ulcer. Perforating or round ulcers are
peculiar to the stomach, and caused by local obstruction of its
blood vessels. Phagedenic ulcers spread rapidly, with great local
irritation, and loss of tissue. Malignant ulcers are characterized
by a rapid, spreading course, with perforation of soft parts, and
resulting in gangrene and sloughing, and necrosis of bone.
The process of healing in ulcers is brought about by granula-
tion and cicatrization, the devitalized parts separating from the
living parts in the form of a thin, ichorous discharge, the exu-
dates beneath and about the walls of the ulcer becoming vas-
cularized and loops of capillary vessels forming and growing
toward the surface. Numbers of leucocytes cluster around these
capillary loops, and thus a healthy surface is formed which dis-
charges a creamy pus-laudable pus.
Cicatrization is a process of skin-growth which covers over
the new granulation tissue, the surrounding surface of skin or
membrane sinking to a level with the granulations and the edge
of the ulcer undergoing change in consistence and color, and the
epithelial cells undergoing segmentation, and growing toward the
centre of the ulcer, which is indicated by a blue film. At the
same time the ulcer is contracting, and continues for a consid-
erable period, and often causes great deformity.
The cicatrix is different from the original substance, having
neither nerves, glands, lymphatics, nor hair, and when injured is
prone to ulcerate.
The causes of ulceration are divided into predisposing and
exciting, local and constitutional. The predisposing causes are