1. After amputations of both upper and lower extremities, the outstanding feature is a generalized osteoporosis in the bones of the mutilated limb, at first patchy but rapidly becoming uniform. It occurs especially near articular ends and muscular attachments and it involves the secondary trabeculae of the cancellous tissue but not the primary architectural features. After lower limb and forearm amputations, rarefaction is obvious in ten days and ceases to progress after three weeks from the date of amputation.
2. After amputations above the elbow, the osteoporosis continues to progress beyond the three-week limit but without destroying the architectural pattern at first. Within a few years there is actual reduction in dimensions of humeral stump, scapula, and clavicle, not explicable on the basis of failure of growth, though precocious union of epiphyses occurs after amputation during or before adolescence.
3. These postamputation phenomena of the upper arm differ from the subsequent changes in infantile and spastic palsy in their erratic distribution and the ultimate disorganization of architecture.