1. Most of the carbon which was injected into the joint cavity was phagocytized by macrophages and leucocytes, and by the tenth day after the injection the greater part of it had been carried out of the joint cavity by these cells.

2. Small amounts of free carbon passed through the intact synovial surface.

3. The synovial lining cells took up small amounts of carbon and tended to hold the ingested carbon indefinitely.

4. A variable amount of carbon was held in fibrin clots which became attached to the synovial membrane and were invaded by cells which formed a new synovial membrane on the free surface of the clot.

5. A small amount of the free carbon was carried from the subsynovial tissues to the popliteal lymph node.

6. Most of the carbon remained in the loose tissues around the joint, and much of it was repeatedly phagocytized and moved about by succeeding generations of macrophages.

7. Living leucocytes were seen to expel ingested carbon but the macrophages apparently retained the material until the cell died and degenerated.

8. The various types of connective tissue and bone cells took up small amounts of carbon and tended to hold it indefinitely.

9. Some of the carbon which was injected into the joint was eventually transported into the femur, tibia, patella, and sesamoid bones.

10. The extracellular carbon in the subsynovial tissues was slowly absorbed as colloidal carbon and was carried by the blood stream to the reticulo-endothelial system.