Egil Skalla-Grimsson was an Icelandic Viking hero that lived during the 10th century and conducted raids and adventures throughout Norway, Sweden, Denmark, the east Baltic lands, England, Saxony and northern Germany. Described by Scientific American as "physically menacing," the stories of Egil state that his skull and facial features were disfigured. The saga also says that Egil's skull was capable of withstanding the impact of an ax, as proved by Egil's descendant Skapti about 250 years after his death, and it is believed that this all because he had Paget's disease — a chronic disorder where the excessive breakdown and formation of bone leads to enlarged and mishappen bones.

[Skapti] picked up Egil's skull and placed it on the fence of the churchyard. The skull was exceptionally large, and its weight was even more remarkable. It was ridged all over on the outside like a scallop shell. Skapti wanted to find out just how thick the skull was, so he picked up a heavy ax, swung it in one hand and struck as hard as he was able with the hammer side of the ax, trying to break the skull. But the skull neither broke nor dented when hit; it simply turned white at the point of impact, and from that result anybody could guess that it could not have been easily cracked by small fry while still covered by skin and flesh.

Physicians have also noted the exceptionally resilient, ivorylike hardness of the afflicted bones. Even the whitening of Egil's skull where Skapti's ax struck is a clear indication of Paget's disease. When subjected to a blow, the soft, pumicelike outer material of the enlarged Pagetic skull gives way to a white, hardened, highly resilient core.

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