Hershel was the son on a German immigrant. His parents died, leaving him to take over his father's job at the factory making lucifer matches. The work was dirty and unsafe, the hours long, and the pay was poor but it was a job and it payed for a room and board at a local hostel. Hershel had long suffered from an infected tooth in his lower jaw, and due to neglect and the constant exposure to phosphorous fumes in the factory, the infection spread. Eventually, medical care was needed, and unfortunately the whole of his lower jawbone was consumed by the infection. Doctors had no choice but to remove the bone and patch Hershel up the best they could.
* see NYTimes, Feb27, 1865 for the full detail of Hershel's story.