cartilaginous or fleshy, or partly of osseous matter, arising from the periosteum and outer shell of the bone, and these often acquire a great magnitude before the diseased mass reaches the interior or medullary part of the bone. SPINA VENTOSA. By this term is understood a mere expansion of a bone from a collection of matter in its substance. The disease may be produced by external injury, exciting inflammation, and consequent suppuration, in the cancellated tissue; or in a weakened and unhealthy constitution, the action may be of a chronic nature. The fluid accumulates, the cancelli are broken down, and the much-attenuated parietes of the bone are pressed outwards. Occasionally inflammatory action is excited on the external surface, from the pressure of the contained fluid, and minute nodules of bony matter are effused, as if nature endeavoured to strengthen those walls which are daily becoming thinner, and more incapable of supporting the weight of those parts which they encircle. The disease differs from Osteosarcoma in the contents being uniformly fluid, generally purulent, though often mixed with more liquid and dark-coloured matter, or with a curdy substance—in the gradual extension of the bone—in no fungus protruding after a portion of the attenuated bone has given way, matter being discharged as from a common abscess; and in the tumour not possessing a malignant disposition. At first there is considerable pain in the part whilst the matter is forming, but afterwards it becomes much less acute, and in many instances there is no inconvenience, except from the bulk of the tumour. Often after having reached no very large size, it becomes stationary, neither recedes or enlarges, and all painful sensations cease; in other cases it enlarges gradually, attains an enormous size, and produces much disturbance of the constitution; but in such instances the patient is generally weak and cachectic. The largest tumour of this species which I have seen, occurred in the lower part of the femur. It measured, in breadth, seven inches, in length, seven and one-fourth. The parietes were composed of an extremely thin lamina of bone, and in this there were numerous deficiencies supplied by delicate ligamentous matter; its cavity was divided into several compartments by thin septa, partly osseous and partly membranous. A representation of the femur so affected is given in the _Practical Surgery_, p. 350. The patient was a boy of twelve years of age; amputation of the limb was earnestly advised, the friends objected, he died hectic. ANEURISMAL TUMOURS.