The new formation of bone in these destructive forms of arthritis conforms in every way to that seen as a result of _septic osteitis_ or periostitis. In other words, the osteophytic outgrowths take origin at the _focus of infection_, wherever that may be, and not, as in _gout_ and _osteoarthritis_, at the _margin of the cartilage_. Still one must recollect that in gout _exostoses_ (Bruce’s nodes) develop sometimes at the _sides_ of the phalanges. These outgrowths are not peculiar to gout, but may be met with in _infective_ forms of arthritis. I am inclined therefore to refer their origin to a local osteitis or periostitis of infective source. That Bruce’s nodes, though not diagnostic of gout, are frequently met with therein, is, I submit, but further evidence of the intrusion of an _infective_ element in the genesis of _gouty arthritis_. _Hypertrophic or Osteo-arthritis._—This is marked by proliferative changes at the margins of the articular ends of the bones. With the advance of the disease the shafts of the related bones become increasingly dense. In _chronic gout_, too, the margins of the cartilages may be studded with little nodules. Radiographically speaking, they cannot be distinguished from those met with in osteoarthritis, save only that they never attain the massive size met with in the latter disorder. The diagnosis in doubtful cases will practically always rest on the clinical history, and more pertinently on the presence of _tophi_. _Rheumatoid or Atrophic Arthritis._—If the changes in the cartilage and bone in osteoarthritis are active and proliferative, these same in rheumatoid arthritis are retrograde and passive in character. In short, hypertrophy of these structures in the former, atrophy in the latter, constitute the distinguishing features. The morbid process in the articular ends in rheumatoid arthritis is one of rarefaction and softening. The cartilage may undergo total or partial absorption, a change to be detected in the very early stages. The bones participate in the pathological change, the first evidence of which is an abnormal translucency to the rays, usually, but not always, confined to that portion of the shaft entering into the joint. Eventually the articular ends of the phalangeal and metacarpal bones may undergo erosion, in some cases to a very marked degree, the bones more or less telescoping into each other.