The deposition of sodium bi-urate is a constant feature of gouty arthritis, but such deposits are not met with in the joints of sufferers from arthritis deformaus unless there has been an antecedent attack of true gout; and if we once abandon the notion that uratic deposits and the presence of uric acid in the blood are necessary elements of gout, we abandon almost the only facts yet established by the study of the pathology, still so obscure, of that disease.
Taking all these points into consideration, it is difficult to suppose that a malady which lacks the distinctive features of both rheuma-, tism and gout should yet be the product of the blending of those two diseases.
The wear-and-tear theory of Arbuthnot Lane, which is based upon the great destruction of the cartilages and bony surfaces, and the grooving of the latter in the lines of the articular movements, is ob viously incapable of explaining the multiple form of the disease, iu which we find the hand-joints early attacked, often in those who have never done hard work of any kind, and in which the lesions show a remarkable tendency to symmetry; and its author now admits this. On the other hand the appearance of the joints post mortem shows that when the articulations are once attacked by the disease, wear and tear plays a prominent part in the production of the ob served lesions.
There is every reason to believe that, as Pye Smith" thinks, the disease is sometimes of the nature of a senile change in the affected joints; in other words, that it is the articular expression Of the ten dency of the tissues of old people to undergo degenerative changes.
There remains to be considered the theory which has gained many adherents of late years, which looks upon the joint lesions of arthritis deformans as dependent upon nervous influences reflex or otherwise, in other words as dystrophic in their nature.
No other argument which has been brought forward in support of this view approaches in cogency to that which is based upon the close similarity of the lesions of arthritis deformans to those found in cer tain forms of articular disease which are developed in the course of organic diseases of the nervous system, such as locomotor ataxia and syringomyelia, and which are generally if not universally held to be dystrophic in their origin. The resemblances and differences be
tween the conditions thus brought into comparison have been already discussed and it is not necessary to describe them further, seeing that their likeness to each other is questioned by none ; so that we may take as established the first point iu the chain of argument in favor of the theory, viz., that the changes iu the joints to which ar thritis deformans gives rise are such as are known to result from dis eases of the nervous system which tend to impair the nutrition of the articular structures.
The remarkable symmetry observed iu the distribution of the lesions in the multiple form of arthritis deformans, a character upon which Senator lays special stress, is also most readily explained by the supposition of a nervous origin. As we have seen, the degree of symmetry attained to is much greater than in other forms of articular disease, but unless we are prepared to assign all symmetrical dis eases to such influences or at least to suppose that the distribution of the lesions is controlled by the nervous system, we must be careful not to press this argument too far. We must not forget that the sub cutaneous fibrous nodules of young rheumatic patients, and various forms of skin disease which are not, like herpes zoster, obviously closely dependent upon nervous lesions, are apt to exhibit a curious symmetry of distribution, which may sometimes be comparable to that shown by arthritis deformans ; nor that in locomotor ataxia at any rate the joints are not particularly apt to-be symmetrically in vaded, although in some other types of organic nerve disease corre sponding joints on the two sides of the body, including the small joints of the hands, are apt to suffer.
The early invasion of the peripheral joints and the general ten dency of the disease to progress centripetally is another feature of the disease which is easily reconciled with a nervous origin.
Further, the 'consideration of the etiology of arthritis deformans shows that its causes are such as might reasonably be expected to give rise to a nervous affection, rather than to a systemic disorder of some other kind.