1. The connexion between the bone and periosteum is so complete that it is not easy to conceive how inflammation of a bone can occur without its membranes being more or less en gaged, and therefore it is difficult to meet with a case of diseased bone unaccompanied by periostitis.
2. The effects of inflammation on the mem brane and on the bone must be different. One structure can swell, the other in the first in stance cannot; and hence the vessels of the bone itself in a state of debility and compressed by an unyielding substance are very liable to die, whilst those of the periosteum tumefy and exhibit a more mitigated form of disease. Thus the periosteum in inflammation is gene rally found swollen or thickened, and detached from the bone underneath, which is then usually either carious or necrosed.
3. Those bones or parts of bones which are hardest and firmest usually die soonest, whence Mr. Wilson's remark that " they are the soonest cured," the process of exfoliation being set up by the surrounding living parts in order to remove that which is dead.
4. In the various processes of repair and re production the periosteum largely participates, and if this latter membrane has been injured or torn off, the vessels of the adjacent cellular tissue seem to assume a new function in order to supply its place. Thus, if a portion of the scalp is torn down, leaving the cranium per fectly denuded, it by no means follows that the bone must exfoliate if the flap has been carefully laid down and still preserves its vitality ; but perhaps the best illustration may be drawn from some cases of necrosis succeed ing to injuries by which the periosteum had been removed, in which the process of regene ration is commenced and completed notwith standing.
Thus far, then, we have seen that there is little difference between the inflammatory process in bone and in any other structure of similar or equal vascular organization ; the chief or cha racteristic peculiarities must therefore depend on the presence of the earthy material, which we shall find influencing the phenomena of the disease, but perhaps more especially its progress. Thus, whether the operation is sana
tive or otherwise—whether adhesion is to be accomplished, ulceration or granulation is to be set up, or a spoiled or dead portion of bone is to be removed—the progress of the work is more sluggish, and its ultimate accomplishment deferred to a much later period, than in any other animal structure. When a bone is wound ed, coagulating lymph is thrown out as quickly and with as much facility as from any other tissue, but nothing can be more familiarly known than that it will require a length of time before consolidation is effected, and the solution of continuity is repaired.
The process of ulcerative absorption in any structure is scarcely understood either as to the stimulus which first determines the vessels to this action or their modus operandi subse quently; still less can we comprehend how a solid unorganized material like the earthy phos phate of bone comes to be thus removed. That this process is not performed with the same facility as in softer structures of equal or inferior vascularity is obvious from the tedious ness of its progress, a delay that is therefore attributable to the presence of this earthy sub stance. The absorption of the earthy particles takes place under two different conditions; one without the secretion of purulent matter (dry caries), examples of which may be seen in the caries of bones compressed by aneurismal tu mours, and in some cases of angular curvature of the spine. It is of importance to remark this kind of caries, and to observe that its pro gress is equally or perhaps more rapid than that in which purulent matter is secreted. Many writers have assumed that pus possessed a solvent quality, and by thus preparing the ossific matter for absorption, materially assisted in the process—an idea which the preceding observation strongly militates against. In the other there is a secretion of purulent matter, and the case is analogous to suppuration and ulceration in the softer tissues, except that the process is still very slow, and in general the odour of the matter is very offensive.