Occasionally abscesses form at a considerable distance from the necrosed part, and terminate in sinuses, which communicate with the diseased bone, and are consequently long and tortuous, so that examination by the probe is rendered difficult. When necrosis is extensive, there is a risk of fracture occurring, if motion of the limb be permitted before a sufficient quantity of matter has been effused, before nature has had sufficient time for the consolidation of her substitute, and consequently before the new bone has come to resemble the old in thickness and cohesion. Violent inflammatory fever attends the incited action of the vessels of the bone and periosteum which precedes necrosis. But after the abscesses have given way the painful symptoms subside, and the health seldom suffers to any great extent, the system becoming gradually accustomed, as it were, to the new condition of the parts. Hectic supervenes only when the disease is very extensive, and joints become involved. Frequently fresh collections of matter form as each piece of bone approaches the surface. When the effusion of new bone has extended to the neighbourhood of a joint, its motion may be very much impeded, and, from the limb being kept in a state of rest for the cure of the necrosis, anchylosis may even occur. _Treatment._—The means of preventing inflammatory action from running high and ending in death of bone have been already alluded to—abstraction of blood, rest, purgatives, and antimonials. When necrosis has occurred, no interference with the bone is allowable, unless the sequestrum is quite loose, or unless the patient’s health is suffering severely under the discharge and irritation. When the sequestrum can be readily moved about, or when, projecting through the external opening, it can be laid hold of by the fingers or forceps, attempts must be made to remove it. The surgeon ought not, however, to allow it to approach the surface, and project externally, for the natural discharge of the sequestrum is a much more tedious process than the removal of it by art, and by the irritation produced during its spontaneous ejection the inflammatory action is continued, and may prove alarming. Long before it has appeared externally, it must have been completely separated from the living parts, so as to admit of ready extraction by the proper means. When it has been ascertained that the sequestrum is separated, it ought to be laid hold of by forceps, and moved freely upward and downward, so that any slight attachments by which it is connected to the neighbouring parts may be destroyed, whether these be minute filaments which still in some degree retain their vitality, or small portions of newly deposited bone, which are so situated as to prevent the free movement of the sequestrum. In general, no impediment of this nature exists, and the dead bone is easily removed. Before extraction can be accomplished, it is generally