pre-Christmas literary guessing game

Tell me the name of the novel:

"Eat and drink," he continually shouted. "Eat and drink, boss, and get warmed up! You sing too, my boy, sing like the shepherds: 'Glory to the highest!... Glory to the lowest...' Christ in born, that's a terrific thing, you know. Pipe up with your song and let God hear you and rejoice."

He had quite recovered his spirits, and there was no stopping him.

"Christ is born, my wise Solomon, my wretched pen-pusher! Don't go picking things over with a needle! Is He born or isn't He? Of course He's born, don't be daft. If you take a magnifying-glass and look at your drinking water- an engineer told me this, one day- you'll see, he said, the water's full of little worms you couldn't see with your naked eye. You'll see the worms and you won't drink. You won't drink and you'll curl up with thirst. Smash your glass, boss, and the little worms'll vanish and you can drink and be refreshed!"