1. The late consequences of stable fractures of the thoracic and lumbar spine have been assessed in a series of workmen. The incidence of symptoms has been recorded and an attempt made to assess the degree of associated incapacity.

2. It has been found that most patients continue to have some symptoms attributable to the back injury and that approximately one in five of the patients who attended for review was partially or completely incapacitated as a consequence of such symptoms.

3. The persistence of symptoms was found to be unrelated to the severity of fracture, to its level, to the presence of radiological evidence of degenerative change, or to the age of the patient.

4. Persistent symptoms were found more commonly in those patients who had received more treatment. The implications of this observation are discussed.

1. Experiments are described in which total infarction of the epiphysis was produced in the metatarsal bones of growing rabbits.

2. After operation both proliferation and normal maturation of the cells of the growth plate were slowed or stopped. Cartilage destruction on the metaphysial side of the growth cartilage continued with consequent thinning of the cartilage. Localised areas of cell death appeared in the growth cartilage as early as the second day after operation. These increased in size and led to revascularisation of the epiphysis by metaphysial vessels which grew through the growth cartilage, reaching the epiphysis seven days after operation. The main, central part of the growth cartilage survived intact and its normal structure was restored after epiphysial revascularisation took place. Vessels growing into the bone from outside also contributed to revascularisation of the epiphysis. After revascularisation occurred, new bone formation led to increased radiographic density of the epiphysis.

1. Experimental defects in the cranial vaults of young adult rabbits were implanted with decalcified, deproteinised and deep frozen homogenous whole bone. The experiments were similar to those of Ray and Holloway (1957) except that these workers used rats as the experimental animals. In addition, six control defects were made and not implanted.

2. All animals were killed six weeks after operation and thirty-four defects were studied by radiology and by histology.

3. All implants became surrounded by connective tissue and in all cases some new bone formed in apposition to implanted fragments. The degree of incorporation of the implants in new bone varied widely, not only between the three implanted groups, but also within each group. In general, new bone formation was greatest in defects implanted with deproteinised and whole bone, least in defects implanted with decalcified bone.

4. The fate of bone implants and the extent to which they can be said to induce osteogenesis are discussed.