The appetite of laborers works for them; their hunger drives them on.

劳力人的胃口使他劳力，因为他的口腹催逼他。

His hunger drove him on. He wondered if Bill, too, were lost. By the middle of the day, the weight of his pack became too great.

饥饿感逼得他太厉害了。他又寻思是不是比尔也迷了路。走到中午时，累赘的包袱压得他受不了。