Suppuration in bones is necessarily connected with loss of substance, and condensation of the surrounding parts; and purulent collections exteriorly, if allowed to press long, or if bound down by unyielding sheaths, will sooner or later produce a breach of continuity, by causing absorption of the outer lamella and the subjacent cancellated texture. A similar effect is produced by aneurismal and some other tumours. Such loss of substance is, in some instances, speedily repaired, after removal of the cause, by effusion of new matter from the surrounding bloodvessels of the bone; thus, in disease in consequence of pressure from large aneurism, there is reason to suppose that the healing process commences as soon as the aneurismal sac begins to diminish, as after operation. But, as has been already observed, the healthy actions are more vigorous in the softer tissues than in bone; and when ulceration has occurred in the latter, it is generally attended with weak action, and presents the same general characters as an ulcer in the soft parts, connected with a feeble action of the bloodvessels; the discharge is thin and fetid, absorption gradually proceeds, and there is little or no effort towards reparation. Cavities in bones are necessarily slower in healing than those in the soft parts; the vitality and power of reparation are lower; and there being no elasticity in the parts, the walls cannot come rapidly together, contract and coalesce. It may tend to prevent confusion of the two different morbid states, if we confine the term ulceration to suppuration in, and absorption of, bone, whilst the vessels retain a considerable power of action, throw out new matter, and procure a reparation of the breach; and this condition of the osseous tissue exists when the disease is situated in the surface of the bone, and when it has been produced by an external cause. On the contrary, the term caries will denote that peculiar kind of ulceration in which reparation is hardly attempted by nature, and is with difficulty obtained by the most active interference; and this disease will most generally be found to affect the cancellated structure. The comparative frequency of one or other of the terminations of inflammation depends much on the kind of bone implicated.