he tooth-germ concerned in their
formation.

The _epithelial odontoma_ is derived from persistent portions of the
epithelium of the enamel organ, and constitutes a multilocular cystic
tumour which is chiefly met with in the mandible. The cystic spaces of
the tumour contain a brownish glairy fluid. These tumours have been
described by Eve under the name of multilocular cystic epithelial
tumours of the jaw.

The _follicular odontoma_, also known as a _dentigerous cyst_, is
derived from the distension of a tooth follicle. It constitutes a cyst
containing a viscid fluid, and an imperfectly formed tooth is often
found embedded in its wall. The cyst usually forms in relation to one of
the permanent molars, and may attain considerable dimensions.

The _fibrous odontoma_ is the result of an overgrowth of fibrous tissue
surrounding the tooth sac, which encapsulates the tooth and prevents its
eruption. The thickened tooth sac is usually mistaken for a fibrous
tumour, until, after removal, the tooth is recognised in its interior.

_Composite Odontoma._--This is a convenient term to apply to certain
hard dental tumours which are met with in the jaws, and consist of
enamel, dentine, and cement. The tumour is to be regarded as being
derived from an abnormal growth of all the elements of a tooth germ, or
of two or more tooth germs, indiscriminately fused with one another. It
may appear in childhood, and form a smooth unyielding tumour, often of
considerable size, replacing the corresponding permanent tooth. It may
cause a purulent discharge, and in some cases it has been extruded after
sloughing of the overlying soft parts. Many examples of this variety of
odontoma, growing in the nasal cavity or in the maxillary sinus, have
been erroneously regarded as osteomas even after removal.

On section, the tumour is usually laminated, and is seen to consist
mainly of dentine with a partial covering of enamel and cement.

_Diagnosis._--Odontomas are often only diagnosed after removal. When
attended with suppuration, the condition has been mistaken for disease
of the jaw. Fibrous odontomas have been mistaken for sarcoma, and
portions of the maxilla removed unnecessarily. Any circumscribed tumour
of the jaw, particularly when met with in a young adult, should suggest
the possibility of an odontoma. Skiagrams often give useful information
both for diagnosis and for treatment.

_Treatment._--The solid varieties of odontoma can usually be sh