Lastly, when we study the changes in structures other than the joints which are associated with this form of arthritis, we find that the visceral lesions which often play so conspicuous a part in blood dis orders are conspicuous by their absence; whereas the changes in the muscles, skin, and other parts are for the most part of a dystrophic type.
The conspicuous atrophy of muscles is doubtless of this nature ; but, as I have attempted to show, these changes are certainly to some extent secondary to the joint changes and attend upon arthritis of all kinds both acute and chronic.
But careful observers have maintained that in arthritis deformaus there is something more than mere arthritic muscular atrophy, and that to some extent at any rate the muscular wasting is not merely secondary to, but advances pa•i passa with the articular disease, and may even be met with in parts in which the joints do not as yet show any signs of being implicated.
Dystrophy of the skin is certainly observed in some cases, as well as disturbances of cutaneous pigmentation and local sweating which are recognized phenomena of nervous disorder, as are also the tin gling and numbness of the hands and feet which are not uncommon early signs of arthritis tleformans.
The most forcible objection to the nervous theory is the absence of any anatomical evidence of disease in the spinal cord to which the dystrophy of the joints can be attributed.
Changes in the peripheral nerves have been found by MM. Pitres and Vaillard in cases of arthritis deformans, and these may play some part in the causation of the cutaneous and muscular changes at least. The observers found that in a case in which mus cular atrophy was very marked the muscular nerves were profoundly affected, whereas in a second case, in which the atrophy was slight, they exhibited no evidences of neuritis. The nerves supplying the diseased joint were but little affected, and MM. Pitres and Vaillard
consider that the joint lesions themselves cannot be ascribed to this cause.
M. Ord believes that a reflex theory best explains the observed phenomena, and that the uterus is very frequently the organ from which proceed centripetal influences which are reflected along the same paths as those which in primary diseases of the spinal cord lead to affection of the joints. In support of this he brings forward evidence of the important part played by uterine disorders in the causation of arthritis deformans, and suggests that predisposing con ditions such as debility and anemia may assist this reflex process by increasing the morbid reflex excitability of the spinal cord provoked by the uterine disorder.
It is obvious that the dystrophic theory of arthritis deformans, although it appears to me to afford the best explanation of the phe nomena of the disease, cannot as yet be looked upon as firmly estab lished, in the absence of further evidence in its support from the side of morbid anatomy, and this obliges us to fall hack upon the hypo thetical explanation of a functional disturbance of the trophic influ ences of the nerve centres.
However, although an hypothesis, it is a satisfactory working hypothesis, which offers an explanation such as uo other theory yet suggested can do, of the development of lesions of identical anatomi cal character under widely different clinical forms.
If in arthritis deformans we have merely a dystrophy of joints associated with dystrophic changes primary and secondary in other structures, it may easily be supposed that such dystrophies will some times be local, limited to a single joint which may or may not have been the seat of injury, may occur iu very chronic forms in the course of senile decay, or under depressant conditions may assume a more generalized form attacking many joints, and adopting a more or less symmetrical distribution.