I. A perfusion technique is described which maintains prolonged (up to six days) survival and metabolic activity of the cells in an excised bone. The perfusate is an acellular tissue-culture medium to which has been added 10 per cent homologous serum and which is oxygenated by a membrane oxygenator.
2. Optimum conditions for perfusion include perfusion pressure of ninety-five millimeters of mercury, flow of 0.15 milliliter per gram of bone per minute. and perfusate Po2 of 250 millimeters of mercury. This will maintain an oxygen utilization of 0.038 m mole per gram of bone per hour, and glucose consumption of 0.10 milligram per gram of bone per hour.
3. Such an isolated bone, in contrast to the similarly isolated spleen does not produce plaque-forming cells after challenge during perfusion with sheep red blood cells. This is in keeping with current concepts of the inability of unaided marrow cells to sponsor antibody producing cells.