Tubercle, when it softens in spongy bones, as in the bodies of the vertebrae, destroys the bone in rounded spots, which are clustered together so as to give it a honeycombed appearance.

The destruction to which the bones of the face and cranium are subject from so-called facial cancer is altogether different from both these processes. Equally unlike them and every other destructive process, it is distinguished by mere negative marks, and may be recognized at the first glance. The surface of the bone and its diploe are successively destroyed by a kind of dissolution or corrosion; nothing is seen in any part but normal bony tissue laid bare; nowhere is there any obvious trace of expansion of the bone, of induration, or of new bony tissue (osteophyte).

The solution in cases of noma (Wasserkrebs, cancrum oris), affects principally the animal part of the bone, and is very similar to that just described; the bone looks as if it had been calcined (Froriep).

But the most difficult point to determine is the changes which are produced in the structure of bone by genuine arthritis. For there are so many anomalies in those affections of the bones which, on the living subject, are attributed to uncomplicated gout, that one is compelled to doubt whether they are all connected with one and the same process. Adventitious growths of various kinds and metamorphoses of apparently syphilitic nature, are ranged together, under this head, with primary indurations, osteoporoses, with consecutive indurations, atrophy, mollities ossium, with different osteophytes, ivory exostosis, etc.

The following changes may, I believe, be looked upon as arising from gout.

There is a metamorphosis in the bony structure of joints, especially in those of the hip-joint, which I agree with some older observers (Portal, Koehler, Austin) in attributing to an arthritic inflammatory process. It is the same as that which the English denominate "malum coxae senile." It presents the following characters.

a. The cavities of joints (acetabula) become enlarged, and mostly flattened.

B. The head or convex part within the joint, acquires a flattened surface, and an overhanging margin: in the instances of the head of the femur, of the humerus, of the radius, etc, it assumes the form of a mushroom.

y. The cartilage which covers the bone is removed, and the cancellous tissue to a varying depth underneath it converted into a dense white, chalky mass, which is polished like marble on its articular surface by constant friction.

§. An exuberant growth of bone takes place around the joint, in the form of a cup-like and warty stalactitic osteophyte; similar masses accumulate outside the joint, which all consist of the same white, chalky substance as the overhanging margin at the head of the bone.

The process by which this change is produced, is a painful one, consisting, without doubt, in an inflammatory rarefaction, swelling and softening of the bone. After furnishing an osseous exudation within the tissue of the bone and all around, - an exudation which may be distinguished by its form and chemical composition, - it terminates in consecutive induration.

It occurs most frequently in the hip-joint, but it is also observed in the shoulder, elbow, and knee, and in the joints of the fingers, and odontoid process. The whole joint becomes misshapen with the excrescences projecting around it.

The disease in the bone is, moreover, sometimes accompanied by similar osseous depositions in the fibrous capsule of the joint, and in neighboring fibrous structures; they assume various forms, like cups or thorns, or are rounded and bossy.

That inflammation seems to me to belong to the same class, which affects long bones, and besides producing induration of their substance, gives rise to a warty and stalactitic osteophyte upon their surface, which renders them rough, like the bark of a tree. And this may be the case also with the osteophyte that grows in cup-shaped, plate-like, thorny or gnarled, processes, in the substance of ligamentous structures near joints, or on the bodies of the vertebrae. They are very often composed of an indurated chalky substance.

Lastly, under circumstances at present unknown, but especially in aged persons, gout produces a painful atrophy, and concomitant brittleness of the bones, rendering them liable to fracture.

Whether rheumatism gives rise to an inflammation that can be distinguished by any definite characters of its products or to any peculiar caries, is not yet ascertained, however positively assertions be made on the point. There is probably no such thing as rheumatic caries. The abscesses upon and within bone, which have been given out as such, I have always recognized as tubercular. Rheumatic inflammation appears generally to attack the periosteum and outermost laminae of the bone, and to produce induration of its tissue, and a warty plated osteophyte on its surface. It is evidently a change closely allied to that which arises from gouty inflammation.