Portions of the cranial bones occasionally die, apparently in consequence of too great a deposition of phosphate of lime obliterating their blood-vessels, the dead part becomes a neutral object, excites irritation, and causes a separation between it and the living portion. When the piece exfoliated is small, it is regenerated by the vessels of the peri cranium, dura matey, and diploe; but when very large, is never regenerated.
If we are permitted to continue the analogy, with which we set out, between the bones and the soft parts, they should be subject to the same varieties of tumours, of the truth of which we have not the least shadow of doubt, particularly when affected symptomatically. At present they are confined to Exostosis (from out, and OTTEGV, a bone), which is divided into various. species by different authors, as true, false, periosteal, medullary, cartilaginous, and fungous exostoses, and sometimes acquire con siderable magnitude. Exostosis chiefly attacks the dense bones, which are thinly covered, such as those of the cranium, inferior maxilla, sternum, clavicle, ulna, and tibia; although all the bones are occasionally affected. The periosteal exostosis is simply a diseased thickening of the periosteum, forming a tumour chiefly attacking the bones of the cranium and tibia, and occurring generally in the syphilitic constitution; but if not attended to, it commonly involves the bone. Sir A. Cooper con siders this affection an osseous deposition between the bone and the periosteum, which adheres firmly to both. In its early stage, it may be removed by the application of the moxa, and the internal ad ministration of the muriate of mercury. Medullary exostosis is when the medulla is primarily affected, and the cancellated structure secondarily; this may be treated in the same manner, but generally re quires the knife. The cartilaginous exostosis is when cartilage forms the nidus for ossific depo sition, which sometimes grows to an enormous size, and frequently attacks the inferior maxillary bone, requiring the removal of more or less of the sound bone on each side. It also takes place on the sternum and ribs, from whence it may be re moved. The fungous exostosis is still softer, con taining spiculte of bone, and being of a malignant nature, acquires occasionally a prodigious magni tude. This is evidently the cellular or laminated osteo-sarcoma of sonic authors, or osteo-sarcosis, or ostco-malakia, or spina ventosa. It attacks the diploe of the cranial bones, the inferior maxillary bone, and the long cylindrical bones. This exostosis can be only cured by the knife, or amputation. Besides these, there is the exostosis eburnea of some authors, a small hard tumour generally situ ated on the os frontis, the exostosis petrosa, and the stalactitieal exostosis. Hydatids are occasionally
found in exostosis. From the magnitude which some of these species of exostosis acquire, they impede the functions of the contiguous soft organs; thus when situated in the antrum, the eye; on the cranium, the brain; on the cervical vertebrae, the spinal cord, and in some eases the subclavian artery; on the inferior maxillary bone, the pharynx and larynx; and on the symphysis pubis, the urethra. Various ridiculous remedies have been recom mended for these tumours, and different instru ments invented; for example, Jeffray's flexible saw, Machell's chain saw, Grade's orbicular saw, and Thal's rotation saw.
Mollities ossium, named also malacosteon, is that disease wherein the bones become so soft that they may be twisted or bent in any direction, and in which, being deprived of their earthy property, as if they had been macerated in-diluted muriatic acid, their animal constituent only remains. When analysed, the quantity of phosphate of lime amounts only to about an eighth. This disease occurs more frequently in women than in men, and generally about the middle period of life. It is preceded by fever and acute pains in the bones, and the urine contains a quantity of phosphate of lime; it is of long duration, Madame Supiot having lived five years. Its treatment is by attention to the early fe brile affection, and afterwards to diet and regimen, exposure to the open air in the horizontal attitude, eold-bathing, flesh-brush and stays.
Rachitis or rickets, which depends also on a defi ciency of the earthy property of bones, is closely allied to mollities ossium, but generally attacks the child, even the feetus in utero. In rickets, the spine and ribs are commonly first affected, and afterwards the long cylindrical bones; the abdomen is tumefied in consequence of the liver, spleen, and mesenteric glands being enlarged; the intestines are filled with flatus, the digestion impaired, the breath fetid and sour, and the stools fetid, acid, and liquid. The respiration is also more or less affected; the head is peculiarly large, with a precocity of intelligence. The singular peculiarity in this disease is, that those children who recover from it in early life and continue strong until adult age, become again af fected with it. The bones, after death, are found lighter, flatter, of a red or brown colour, porous, spongy, soft, compressible, and vascular; the cra nial are thicker, the long bones thinner, and the medulla is like reddish serum. For the treatment, and a fuller account of this disease, the reader is referred to the Article MEDICINE, VOL XIII. p. 2 9 .