(A) Section of a graft in a control specimen. Bone ingrowth has ocurred from the lower end of the picture and upwards. The bone formation frontier has reached roughly halfway through the graft (arrows). Behind the frontier a marrow cavity has formed, and inside the cavity the graft is almost entirely resorbed. (B) Section of a graft in a rat treated with the high dose of alendronate. The ossification has reached the same distance (arrows), but the graft is not resorbed. Hematoxylin Eosin, bar lengths 1 mm.