This study shows that after intra-articular injection, aurothiomalate and colloidal gold of small (200 A) particle size were rapidly absorbed from joints while the larger, 300 A, particle size colloidal radioactive gold could not be found outside them. Larger particle size suspensions seem therefore more likely to remain localised in the joint and its lining synovium after intra-articular injection, the systemic absorption from the joint cavity diminishing with increasing particle size. It was also found that the intra-articular injection of small amounts of aurothiomalate, of colloidal gold and of colloidal radioactive gold produces identical degenerative lesions in the lining cells of the proximal convoluted tubules of the kidneys. These lesions were always found, although gold particles were demonstrated only in sampled kidney tissues of the animals injected with the soluble gold preparation whereas no gold could be detected in the tissues of animals injected with colloidal non-radioactive or radioactive gold. Electron microscopic evidence is presented to suggest the possibility that the mitochondria are the "target" organelles of the gold-induced cellular damage. Mitochondrial damage was demonstrated in liver and spleen in addition to the already described kidney damage. The correlation between structure and function of the mitochondrial changes is not clear, and ionic shifts may be both a cause and a result of damage.

1. A survey of 112 cases of residual poliomyelitis with leg shortening of 2·5 centimetres or more is reported.

2. In eighty-seven patients paralysed in early infancy the fibular shortening was greater than the tibial shortening.

3. The absence of the normal "to and fro" motion of the fibula causes delay in the appearance of the fibular epiphyses and retards fibular development.

4. The shortening of the fibula in infancy causes deformity at the ankle, in the tibia itself and at the knee.

5. At the ankle the poorly developed lateral malleolus causes wedging of the lower tibial epiphysis and valgus at the ankle, which is often unstable.

6. At the knee progressive genu valgum is produced and in the tibia lateral torsion occurs.

7. The clinical significance of these deformities in relation to reconstructive procedures is stressed.

1. In the experiments undertaken autogenous vesical mucosal transplants were made in guinea-pigs. The transplanted mucosa proliferates and forms a nodule. Central necrosis of the nodule and the secretion of the proliferating epithelium combine to form a cyst filled with a viscous fluid.

2. Before the cyst is well defined some of this fluid diffuses into the sub-epithelial connective tissue, producing areas of tissue oedema which later are transformed into translucent hyaloid islands. With further condensation of the collagen fibres, these areas are converted into primitive bone. The hyaloid islands act as a bone precursor. Bone always formed in the wall of the cyst within thirty days except in cases of sepsis or death of the transplant, when there was no osteogenesis. Homografts of vesical mucosa were found unreliable in their capacity to induce bone.

3. The results of the histochemical investigation and radiographic diffraction of the hyaloid areas suggest that the proliferating mucosa is the source of the inducing agent.

4. Bone can be induced only in sites where a primitive vascular connective tissue is growing and where there exists an adequate blood supply.

5. The rapid rate of osteogenesis can be seen in the radiographs of induced bone in radial defects. The electron-microscopic study of the induced bone at three weeks confirmed that osteoid had been formed so quickly that calcification had not yet taken place.

6. The relationship between the bone induced by transplanting vesical epithelium and the formation of urinary calculi is discussed and their common origin postulated.

1. A family of six generations, consisting of 114 members affected by epiphysial dysplasia of the lower extremities, is described.

2. Twenty-two males and twenty-three females were affected, while thirty-two males and thirty females were unaffected. Seven members of the family could not be traced.

3. Variations from Fairbank's description of dysplasia epiphysialis multiplex are discussed. In the family here reported the lower limbs only were affected and the severity of the disease was very variable.

4. Long term follow-up studies are presented.

1 . Sloughing of homogenous skin grafts and clouding of corneal transplants have been shown to be due to antigen-antibody reaction; antigens A and B have been demonstrated in human epidermis and corneal tissue; and anti-red-cell agglutination has been observed in dogs after homogenous bone transplantation. Human bone was therefore examined in thirty-three experiments to determine the presence or absence of A and B antigens.

2. The bone was separated into hard cortical bone, hard washed cancellous bone and soft-tissue washings of bone.

3. Adsorption experiments showed that A and B antigens are absent from cortical bone. A and B antigens are present in cancellous bone.