which produced epilepsy and idiocy. Bidder found an irregular denticulated osteoma four centimeters in diameter in the left corpus

FIG. 304.-Exostosis of the femur (after Orlow): its surface was clad with cartilage and surmounted by a bursa.

striatum. The patient was the subject of contracture of the left arm and leg since infancy, the left leg being shortened two centimeters. In the case reported by Ebstein the tumor was located in the cerebellum and produced no symptoms. In operations upon the brain for epilepsy or other focal or cerebral symptoms osteoma as a possible cause should be remembered.

Epiphyses of the Long Bones.-By far the greatest number of osteomata occur in the epiphyses of the long bones. Their origin is similar to that of chondromata in the same locality, only that in this instance the chondroblasts undergo a higher degree of development and the chondroma is transformed into an osteoma. Syme met with cases of epiphyseal osteoma in which the tumor was surrounded by a sort of synovial capsule; in other cases the tumor projects into the joint. Epiphyseal osteomata are often multiple like the chondromata, and are nearly always covered by a thin crust of cartilage, resembling in this respect the articular extremities. The tumors, which are composed of cancellous bone-tissue, are often supplied on their surface with a bursa interposed between the tumor and the fascia, tendons, or muscles overlying it. Occasionally an osteoma is pedunculated, and frequently it has a broad base. The tumors are painless, but they often produce pain by pressing on adjacent nerves.

A favorite locality for osteoma is above the inner condyle of the femur (Fig. 304), close to the insertion of the adductor magnus. In this locality the tumor is peculiarly apt to acquire a narrow, pedunculated base. The pedicle of such a tumor may occasionally fracture, as happened in the cases reported by Paget and Lawrence. Epiphyseal osteomata, unless of great size, seldom interfere with the functions of adjacent parts, and unless this is the case operative treatment is contraindicated.

Muscles and Tendons.-Osteomata are occasionally found in soft parts as distinct and discontinuous tumors invested with capsules of

connective tissue. Paget refers to a tumor of soft cancellous tissue occupying the dorsal surface of the trapezial and scaphoid bones, completely isolated from them and from all the adjacent bones. In the museum of St. George's Hospital, London, is a tumor formed of compact bony tissue that lay over the palmar aspect of the first metacarpal bone, loosely imbedded in the connective tissue, and easily separated from the flexor tendons of the fingers.

Exostoses tendineæ have frequently been observed. The bony growth originated in the tendon, independently of the bone to which the tendon was attached. Folk removed an exostosis apophytica which was attached with a broad base to the sacrum and which terminated in a conical projection several inches in length in the gluteus maximus.

Seat of Fracture.-Under certain circumstances the callus in the repair of a fracture is so profuse that a large bone-tumor remains after consolidation has been completed. Van Heerkeven applied to this condition the term callus luxurians. A good example of this condition is furnished by the bony hyperplasia which often occurs around a fractured rib in a lower animal. Such enormous permanent callus-formation has been observed by König and others as one of the remote results of fracture. In some cases it has been impossible to make a differential diagnosis between an osteoma at the seat of fracture and an osteo-sarcoma. The tumor under such circumstances springs from a post-natal matrix of osteoblasts produced by the injury. The difference between a superabundant callus and an osteoma at the seat of a fracture is that in the former case the provisional callus disappears or is at least greatly diminished in size, while an osteoma remains permanently as a bone-tumor. The operative removal of such an osteoma may become necessary if the tumor implicates important muscles, vessels, or nerves. An operation should not be undertaken until by the clinical course the true nature of the tumor has been revealed, by which means only is it possible to make a differential diagnosis between a superabundant provisional callus, an osteo-sarcoma, and an osteoma. Orbit. Osteoma of the orbit occurs either as a primary tumor, when it is attached to the bony wall of the orbit, usually on the nasal side, or the tumor reaches the orbit from the frontal sinus or from the antrum of Highmore. In the latter case the appearance of the tumor in the orbit is usually preceded by signs and symptoms which point to its primary location in either of the adjoining cavities. In a case of orbital osteoma that recently came under the observation of the writer, considerable exophthalmus was observed and the eye was displaced outward. Beneath the orbital arch a hard tumor could be felt under the upper eyelid, at the inner angle. The tumor, which was exposed by

an incision along the superciliary arch, was an inch and a half in length, and was attached to the inner wall of the orbit by a contracted, almost pedunculated, base. The tumor was detached from the bony wall with a narrow chisel, and was removed without inflicting any injury upon the more important contents of the orbit. The eye after the operation gradually resumed its normal position. If the tumor is located primarily in the frontal sinus or in the antrum of Highmore, its removal must be preceded by a temporary resection of the anterior wall of the cavity in which it is located.

Eye.-Schiess-Gemuseus collected eight cases of osteoma of the eyeball. In each case the tumor occupied the elastic lamella and the choroid capillaries.

Subungual Osteoma.-The last phalanx of the great toe is not infrequently the seat of a subungual osteoma. It always grows on the margin, and usually on the inner margin, of this bone. The tumor projects under the edge of the nail, lifting it up, and thinning the skin. that covers it until an excoriated surface is presented at the side of the nail. The growth of the tumor is usually very slow, and when it has reached a diameter of from one-third to one-half an inch it becomes stationary. The extirpation of subungual osteoma with cutting-forceps must be preceded by partial or complete removal of the nail.

XXII. ODONTOMA.

Definition. An odontoma is a tumor composed of dental tissue in varying proportions and in different degrees of development, arising from teeth-germs or from teeth still in the process of growth. This definition and the description of the different varieties are gleaned from Sutton's excellent work on Tumors, which contains the most accurate account of tumors of dental origin.

Sutton's Classification of Dental Tumors.—

1. Epithelial odontome, from the enamel-organ.
2. Follicular odontome,

3. Fibrous odontome,

4. Cementome,

5. Compound follicular odontome,

from the tooth-follicle.

6. Radicular odontome, from the papilla.

7. Composite odontome, from the whole gum.

I. Epithelial Odontomes.-These tumors occur, as a rule, in the mandible; but they have been observed in the maxilla (Sutton). They are encapsulated and contain numerous small cysts. In color they resemble myeloid sarcoma, for which they have been mistaken. They consist of branching and anastomosing columns of epithelium, portions of which form alveoli. Although they may occur at any age, they are most frequent at the age of puberty.

2. Follicular Odontomes.-The follicular odontomes are the dentigerous cysts. They occur commonly in connection with teeth of the permanent set, and especially with the molars. The tumors often attain large size. The wall of the cyst may be very thin, so that it crepitates under pressure. The cavity contains a viscid fluid and the encysted tooth, which is often imperfectly developed.

Dentigerous cysts rarely suppurate. Three cases of follicular odontome have come under the writer's observation. In one case the cyst was as large as an orange, and contained an imperfectly developed molar tooth and a clear viscid fluid. In the second case a fistulous opening led into the bone above the permanent molars, and necrosis of the maxilla was suspected. The patient had been treated for a long time for suppuration of the antrum. At the bottom of the cyst part

of a molar tooth was found.

A follicular odontome invariably occurs in connection with teeth the eruption of which is retarded or prevented owing to their being developed in an abnormal position, whereby they become impacted by the surrounding bone. These tumors appear at a period of life succeeding that at which the alveolar portions of the maxillæ are in a state of active development, in which they readily furnish an amount of bone sufficient to perfectly envelop the tooth. The capsule of the tooth, the remains of the enamel-organ, has been shown by Tomes to be, after the calcification of the enamel, quite free and detached from that structure, and therefore, being attached only to its surroundings, will be carried away from the surface of the enamel with them; there will thus be left a space into which, as a matter of course, serous fluid must under atmospheric pressure be effused, and thus there is formed a cyst, the walls of which will be the dental capsule, including the projecting crown of the tooth (Coleman).

3. Fibrous Odontomes.-The fibrous capsule of a tooth, composed of an outer firm wall and an inner loose layer of tissue, may become thickened, constituting with the contained tooth a fibrous odontome. Such a tumor is often mistaken for a fibroma, especially if the tooth be small and ill-developed. Under the microscope fibrous odontomes present a laminated appearance with strata of calcareous matter. Rickets appears to play an important part in the production of fibrous odontomes.

4. Cementomes. -A cementome is a fibrous odontome which has undergone ossification. The tooth in such cases is encapsuled in a mass of cementome. Cementomes occur most frequently in horses. Tomes describes a tumor of this kind which weighed ten ounces. Sutton refers to one which weighed seventy ounces.

5. Compound Follicular Odontomes." If the thickened capsule ossifies sporadically instead of en masse, a curious condition is brought about, for the tumor will then contain a number of small teeth or denticles consisting of cementum or of dentine, or even ill-shaped teeth composed of three dental elements-cementum, dentine, and enamel" (Sutton). As many as four hundred denticles have been found in a single tumor. Tumors of this character have been seen in the human subject. Tellander met with a case in a woman aged twenty-seven.

6. Radicular Odontomes." This term is applied to odontomes which arise after the crown or the root has been completed and while the roots are in the process of formation" (Sutton). In the specimen represented in Figure 305 the outer layer of the tumor is composed of cementum; within this is a layer of dentine, deficient in the lower part of the tumor; and inside this dentine is a nucleus of calcified pulp. number of radicular odontomes have been observed in the human subject. Suppuration is a common complication of these tumors.

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