BONE, PATHOLOGICAL CONDI TIONS OF.—The bones, as the foundations of the animal system, as the passive organs of loco motion, required necessarily to be firm and com paratively inelastic and unyielding, qualities which we have seen in the preceding article are imparted to them by the addition to their original animal elements of a saline or earthy substance, consisting principally of phosphate of lime. It is obvious that this difference of structure and constitution must have considerable in fluence in modifying the diseases to which they are liable, and in giving to the affections of these organs many of their distinguishing peculiarities. In considering, therefore, the phenomena exhibited in the various patholo gical conditions of the osseous system, not only must the presence of this unorganized earthy substance be constantly borne in mind, but even its relative amount, its abundance or deficiency must command attention. In early life, when the animal material preponderates in quantity, the bones are highly yascular, and comparatively soft, flexible, and springy, and though liable 'to many serious diseases, they are very apt to escape the effects of injury : fracture uncommon in infancy; and in child hood the bones, bending rather than breaking, often exhibit that partial fracture which has been likened to a " branch of a tree that yields to an attempt to break it while it still retains its sap." The powers of repair are commensurate with the extent of vascular or ganization at this period ; fracture is quickly re-united, and its effects so regulated by the subsequent grovvth of the bone that permanent deformity is a very infrequent occurrence.
But this activity in the osseous system in early life has its evils. The period of youth, between absolute childhood and puberty, is that in which disease is most easily and, there fore, most frequently developed, and although extensive powers of reparation are constantly exhibited in recovery after caries, in re production after necrosis &c., still are the operations that lead to these results languid and too often inefficient,—circumstances that may be attributed partly to peculiarity of or ganization in the structure affected, but per haps with more propriety to the influence of some general constitutional taint over which medicine exerts but slender control.
The osseous system cannot be considered as having attained maturity until a period sub sequent to the age of puberty, most commonly somewhere between the twenty-seventh and thirtieth years. At this time bone is calculated most perfectly to answer its purposes in the animal economy : it is then least liable to disease ; and if fractures and other injuries are more frequent, it is only because indivi duals are now more exposed to them. The effects of these injuries are in general repaired sufficiently well, but if deformity has been produced it will be permanent, because the bone has ceased to grow.
As life advances, the osseous system un dergoes many obvious alterations. The shape of some bones is altered : the natural curvatures of the long bones, for example, are increased; the direction of the processes and parts of others is changed, the most remarkable example of which occurs in the neck of the thigh-bone ; and their powers of affording sup port and resisting violence are obviously en feebled. This senile fragility has been gene rally supposed to arise from an increase in the earthy material of the bones. The opinion, however, has not been invariably borne out by the results of chemical analysis of bones at different periods of life, and has been objected to by M. Ribes,* who, after extensive obser vation and enquiry, was led to believe " that the fragility of bones depended essentially on a change of action being established within them, and that all the parts entering into the texture of bones are really in less quantity in the aged than in younger individuals." If by " a change of action" in the above passage is meant that gradual decrease of the vital properties observed in every organ and in every tissue as man declines into the vale of years, we cordially agree in the opinion ; being satisfied that the results of chemical or me chanical enquiries, however true in themselves, will always be insufficient to explain the ope rations carried on within a living body.