Osteomata.—Osteomata are composed of tissues more or less resembling bone in their microscopical structure. Inter mediary forms are known as of the com pact variety. When very dense, they are spoken of as eburnated; when loose in structure, as spongy or medullary osteo mata. They are usually found in the neighborhood of bone, but may occur as heteroplastic growths: i.e., in those situ ations, as in the lung, where no bone is normally found. Osteophytes are spicu lated processes usually attached to bones, but are also found elsewhere, as in the falx cerebri, where they are quite com mon and are due to an internal ossifying pachymeningitis. More extensive and more tumor-like roughened prolonga tions from bones are spoken of as ex ostoses; circumscribed patches within the bone are called enostoses; periosteal exostoses, when in the periosteurn, but separated from the bone; are named parosteal osteomata, when near the bone and disconnected; osteoma when still farther away.
In the eburnated variety the growths may be single or multiple, and are found especially in the flat bones of the skull. The lamelhe follow the outline of the tumor, and contain no blood-vessels or Ilaversian canals, though narrow cana liculi are found. The compact osteoma may be found in the meninges of the brain, in the choroid of the eye, in the pericardium, etc. The vessels and Ha version canals run at right angles to the long axis of the bone. In the spongy form tfaversian systems are seen, and the character of the growth is like that seen on the extremities of the long bones. They assume the greatest variety of forms, and combine as osteofibroma, osteochondroma, osteochondrosarcoma, and osteosarcoma. When combined with sarcomata, they may give metastasis, which sometimes even appear on the skin. The continuous exercise of a mus cle, as by drilling with the gun, or in horseback-riding, may give rise to osseous formations in the muscle. )Iyositis os sificans is a peculiar progressive disturb ance of the muscular connective tissue occurring in early youth.
Odontomata.—These tumors have been but little studied and are often classed among the osteomata or dermoids. They are made up of dental tissues in different amounts and in different degrees of de velopment. Thus, there may be teeth germs other than these normally to be developed, and these may undergo pro liferative changes in any of their com ponent parts. A tooth may grow upward into the antrum of Highmore and there develop into an odontoma. These tumors are rarely diagnosed before operation, and unnecessarily severe operations, as excising a portion of the mandible, are sometimes practiced where mere removal of the tooth or enucleation of the tumor is all that is required for their cure, as they are not malignant. Odontomata are
found in early adult life. They also occur in the lower animals, as in the horse.
Fibromata.—Fibromata are composed of connective tissue; if rich in cells, they are spoken of as soft, and scrapings show spindle-formed cells; if made up largely of bundles of fibrils, they are called hard. They occur as nodular, capsulated tu mors, sharply defined from the surround ing tissues, and are especially common in the colored race. They may assume the form of polyps 01 papillomata at the junction of epithelial and mucous sur faces, as in the vagina. On section the larger nodes are white and glistening, and arc seen to be made up of smaller nodes arranged concentrically; cutting gives rise to a peculiar, creaking noise. Fibrous tissue is widely distributed throughout the body; hence, as would be expected a priori, these tumors occur in the most diverse situations. In the breast the peri canalicular variety is often found. They are frequently multiple, especially in the uterus and the skin, and stain well with picrocarmin. Areas of softening often occur, due to fatty degeneration, myx omatous changes, etc. They sometimes show dilated blood-vessels and lymph channels, and in the uterus are pecul iarly liable to undergo calcareous infil tration. In the uterus they are often combined with myoma. Elephantiasis, though attended with much overgrowth of fibrous tissue, should not be classed here, as it is due to the mechanical ob struction of the lymph-channels.
Keloids.—These are peculiarly dense forms of fibromata, and most often fol low wounds, sometimes so small as to have escaped notice. They are sometimes very troublesome on the face, neck, and breast of colored persons. They are also seen in the spleen. Extensive thicken ings of the serous membranes, such as the pleura, are the remnants of old in flammatory lesions.
Myxomata.—These tumors are largely composed of mucoid tissue. The cells are branched and irregular, their pro longations interweaving the one with the other. On section the surface is more or less transparent and the blood-vessels can be seen beneath the surface. Myx omatous fluid coagulates upon the addi tion of water. These tumors are never composed entirely of myxomatous tissue, as they must have a frame-work upon which to be formed. The best-known varieties are fibrornyxoma, lipomyxoma, chondromyxonia, and myxosarcoma. Fi brous, fatty, cartilaginous, and sarcoma tous tissue may undergo myxomatous de generation. Myxochondromata are espe cially common in the parotid.