In the foregoing pages we have presented specimens illustrating in detail the several stages of healing bone in amputation stumps.

Within five or six days from the date of operation (W. R. U. 262) the cut surface is rarefied by increased vascularity so fine that, though it is obvious in the roentgenogram, it cannot be seen on the specimen except under magnification. This erosion gradually obliterates the saw cuts and rounds off the margins of the cut face.

By the lapse of eleven days after operation (W. R. U. 864) the erosion, unequally progressive and still permitting evidence of the saw cuts, is plainly most active in those areas of the cut shaft which are thinnest and least injured.

After thirteen days (W. R. U. 319) the saw cuts may be entirely obliterated and callus, both periosteal and endosteal, well developed.

If the amputation has taken place through cancellous tissue and not through the marrow cavity, the lapse of fifteen days (W. R. U. 1019) is enough to permit fair healing with even the commencing appearance of waxy textured bone on the face of the stump.

But if the marrow cavity be opened, seventeen days later the canal is still quite patent, though narrowed somewhat by the development of concentric rings from the endosteal callus (W. R. U. 1585).

After several weeks the endosteal callus has formed an imperfect cap for the medullary cavity and the vascular channels on the eroded cut face are narrowed (W. R. U. 952). This is soon followed by the closure of the vascular channels and by a wax-like transformation of the texture of the new bone (W. R. U. 1519, W. R. U. 1217).