Sentence:  Look at Adam through the rest of the day, as he stands on the scaffolding with the two-feet ruler in his hand, whistling low while he considers how a difficulty about a floor-joist or a window-frame is to be overcome; or as he pushes one of the younger workmen aside and takes his place in upheaving a weight of timber, saying, "Let alone, lad! Thee'st got too much <WSD>gristle</WSD> i' thy bones yet"; or as he fixes his keen black eyes on the motions of a workman on the other side of the room and warns him that his distances are not right. 
Meaning of the word marked with <WSD> tags:  Bone not yet hardened by age and hard work.