given way, the tumour projects through the aperture, contaminating the adjacent soft parts, imparting to them a morbid action, and extending also in the cancellated tissue of the shaft of the bone. In some cases, the integuments are tense and discoloured, with large vessels running on their surface; the tumour feels soft and fluctuating, though the skin may not ulcerate till long afterwards. Perhaps the most common seat of this disease is the under-jaw, but it may occur in any of the bones; when it has been of chronic duration, not one bone but several are affected; and in one case which I saw, the disease commenced in the under-jaw, which it deformed to a frightful degree; almost every bone in the body was similarly, though less extensively diseased; this could be readily observed during the life of the patient, and was confirmed by dissection. From this, it appears, that the affection is not only dependent on local causes, but connected with a morbid state of the constitution, predisposing to it, and cooperating with its exciting cause. There are other tumours of bones in some degree resembling, which do not strictly come under the term Osteosarcoma. Some are wholly cartilaginous, the disease commencing in their centre, and involving their entire substance, emitting a gelatinous fluid when cut, but containing no cells; others are not uncommon, partly osseous, and partly cartilaginous, containing cells filled with a glairy fluid; others are composed of cartilage, intersected with dense fibrous matter, in a greater or less proportion. In fact, the individual tumours of bones vary as much from one another as those of the softer tissues; scarcely two are alike in their progress, action, or anatomical characters. Irregular spicula of bone are found in many parts of their structure; in the same way that portions of bone often exist in tumours having no connection with the bones; in many places they are softened and broken down, the partitions between the cells are destroyed, and these contain a pulpy mass of a dark sanious appearance. On making a section, they are observed to be continuous with the interior of the bone, which is converted into a substance similar to themselves, or is of a more soft and medullary character. The external surface becomes tuberculated, the integuments are painful, and changed in appearance; they ulcerate, the tubercles burst, the discharge is thin and bloody, the ulceration extends; not unfrequently a fungus protrudes, and occasionally bleeds; this may slough, the tumour becomes farther exposed, portions of it die, and are discharged, unhealthy fungous granulations project from amongst the cancelli of the tumour, and emit a sanious putrid discharge, often bloody; severe constitutional irritation accompanies this state, the patient becomes hectic, is much exhausted, and sinks, unless the morbid parts be removed. There are also tumours of bones, composed partly of