I have never had any chance of examining the growth _post mortem_, but
the portions which I have removed _en masse_ by operation have enabled
me to make some investigations. The periosteum strips off readily, and
under this is a thin shell of compact bone, which appears somewhat
ridged on the side towards the periosteum. The rest of the tumor
consists of cancellous bone. The whole swelling cuts readily with bone
forceps and consists of quite soft bone. On making microscopical
preparations there were signs of ossification in membrane proceeding
under the periosteum, and the rest appeared like ordinary wide-meshed
cancellous bone. The whole process appeared to be that of a slow
“osteoplastic periostitis.”