An investigation of the routes of venous escape from the diaphyseal marrow of the canine and rabbit long bones.

The routes of venous escape from the diaphyseal marrow have been demonstrated by directly perfusing the marrow cavity of canine and rabbit long bones with barium sulphate suspension. Plain radiographs immediately after perfusion revealed prompt escape of dye into the systemic veins via a number of large transcortical emissary veins. A central venous sinus as usually described was not found; instead the dye occupied the whole of the medullary cavity extending from metaphysis to metaphysis. This suggests that the marrow is an open circulatory system with ill-defined boundaries. Radiographs of thin sections of the perfused bone after decalcification, which permitted visualisation of the fine vessel arrangements, revealed numerous haversian venules. These drained the marrow into a separate extraosseous venous network on the surface of the bone.