Photomicrography of fracture callus from rat femur. Panoramic views (1) and high magnification (20×) photomicrography (2) of fracture healing and callus formation was illustrated using calcified bone histology technique with toluidine blue staining. The magnification points up the remodelling zone within the fracture gap. 28 days after fracture the fracture gap (*) and a sufficient callus is noticeable with partial bony bridging (A + B). 49 days after fracture the femurs demonstrate increased bone tissue with lamellar bone (C + D). No significant difference could be seen between control and treatment group. Bar represents 1 mm (A1 – D1) or 100 μm (A2 – D2) respectively. pbb = partial bony bridging; lp = lamellar part; wp = woven part.