Sentence:  I was once, I remember, called to a patient who had received a violent contusion in his tibia, by which the exterior cutis was lacerated, so that there was a profuse sanguinary discharge; and the interior membranes were so divellicated, that the <WSD>os</WSD> or bone very plainly appeared through the aperture of the vulnus or wound. 
Meaning of the word marked with <WSD> tags:  Bone.