Figure 2. Comparison of the progression of healing in fractures and distraction osteogenesis. Murine femur fracture calluses and tibia distraction gap tissues were prepared at the indicated time-points. The different stages of healing and bone formation are given for each. Representative histologic specimens are stained with Safranin-O/fast green, which stains cartilage bright red. The scale bar in the lower right indicates 1 mm for all panels.